Photosensitive composition, compound for use in the photosensitive composition and pattern forming method using the photosensitive composition

ABSTRACT

A photosensitive composition for use in the production process of a semiconductor such as IC, in the production of a circuit substrate of liquid crystal, thermal head and the like or in other photofabrication processes, a compound for use in the photosensitive composition, and a pattern forming method using the photosensitive composition, are provided, which are a photosensitive composition excellent in the sensitivity, resolution and pattern profile, assured of large exposure latitude and small pitch dependency, and improved in the sensitivity and dissolution contrast at the exposure with EUV light, a pattern forming method using the photosensitive composition, and a compound useful for the photosensitive composition.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a photosensitive composition capable ofchanging its properties by undergoing a reaction upon irradiation withactinic rays or radiation, a compound for use in the photosensitivecomposition, and a pattern forming method using the photosensitivecomposition. More specifically, the present invention relates to aphotosensitive composition for use in the production process of asemiconductor such as IC, in the production of a circuit substrate ofliquid crystal, thermal head and the like, in other photofabricationprocesses or in the lithographic printing plate or acid-curablecomposition, and also relates to a compound for use in thephotosensitive composition and a pattern forming method using thephotosensitive composition.

2. Background Art

The chemical amplification resist composition is a pattern formingmaterial capable of forming a pattern on a substrate by producing anacid in the exposed area upon irradiation with actinic rays or radiationsuch as far ultraviolet light, and through a reaction using this acid asthe catalyst, causing the area irradiated with actinic rays or radiationand the area not irradiated therewith to change in the solubility in adeveloper.

In the case of using a KrF excimer laser as the exposure light source, aresin having small absorption in the region of 248 nm and having a basicskeleton of poly(hydroxystyrene) is primarily used as the main componentand this is an excellent system capable of forming a good pattern withhigh sensitivity and high resolution as compared with conventionalnaphthoquinonediazide/novolak resin systems.

In the case of using a light source of emitting light at wavelengthsshorter than that, for example, in using an ArF excimer laser (193 nm)as the light source, a satisfactory pattern cannot be formed even by theabove-described chemical amplification system because the compoundhaving an aromatic group substantially has large absorption in theregion of 193 nm.

In order to solve this problem, a resist containing a resin having analicyclic hydrocarbon structure with high transparency has beendeveloped for use with an ArF excimer laser. However, the alicyclicstructure generally has low polarity, and the reactivity fordeprotection in the resin is greatly decreased as compared with that inpoly(hydroxystyrene). Therefore, an acid having high acidity isnecessary for the image formation and a specific organic sulfonic acidis used, for example, in Patent Document 1 (JP-A-2002-131897 (the term“JP-A” as used herein means an “unexamined published Japanese patentapplication”)), Patent Document 2 (JP-A-2003-149812), Patent Document 3(JP-T-11-501909 (the term (the term “JP-T” as used herein means a“published Japanese translation of a PCT patent application”)), PatentDocument 4 (JP-A-6-242606), Patent Document 5 (JP-A-11-160861) andPatent Document 6 (U.S. Patent Application 2004/0087690A1).

However, many points still remain unsatisfied, and more improvement isdemanded with respect to the sensitivity, exposure latitude, patternprofile, pitch dependency, and the like.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a photosensitivecomposition excellent in the sensitivity and resolution and improved inthe exposure latitude, pattern profile and pitch dependency, a compoundfor use in the photosensitive composition, and a pattern forming methodusing the photosensitive composition.

The present invention is as follows.

1. A photosensitive composition comprising (A) a compound capable ofgenerating an organic acid having a bond which is cleaved by an acid,upon irradiation with actinic rays or radiation.

2. The photosensitive composition as described in the item 1, whichcomprises (A) a compound capable of generating an organic acid having astructure represented by the following formula (I) upon irradiation withactinic rays or radiation:

3. The photosensitive composition as described in the item 1 or 2, whichcomprises (A) a compound capable of generating an organic acidrepresented by the following formula (II) upon irradiation with actinicrays or radiation:HO₃S-A-X-B-R  (II)wherein

A represents a divalent linking group,

X represents a single bond or —SO₂—,

B represents a single bond, an oxygen atom or —N(Rx)-,

Rx represents a hydrogen atom or a monovalent organic group,

R represents a monovalent organic group containing a nitrogen atom, saidnitrogen atom being substituted by the following formula (III):

R′ represents a monovalent organic group, and

when B is —N(Rx)-, R and Rx may combine to form a ring.

4. The photosensitive composition as described in the item 3, whereinthe compound (A) capable of generating an organic acid represented byformula (II) upon irradiation with actinic rays or radiation is asulfonium salt compound of the organic acid represented by formula (II)or an iodonium salt compound of the organic acid represented by formula(II).

5. The photosensitive composition as described in any one of the items 1to 4, which further comprises (A′) a compound capable of generating anacid compound other than the organic acid, upon irradiation with actinicrays or radiation.

6. The photosensitive composition as described in the item 5, whereinthe compound (A′) is a sulfonium salt of fluorine-substitutedalkanesulfonic acid, fluorine-substituted benzenesulfonic acid or afluorine-substituted imide acid.

7. The photosensitive composition (positive photosensitive composition)as described in any one of the items 1 to 6, which further comprises (B)a resin capable of decomposing under the action of an acid to increasethe solubility in an alkali developer.

8. The photosensitive composition as described in the item 7, whereinthe resin (B) has a fluorine atom in the main or side chain.

9. The photosensitive composition as described in the item 8, whereinthe resin (B) has a hexafluoroisopropanol structure.

10. The photosensitive composition as described in any one of the items7 to 9, wherein the resin (B) has a hydroxystyrene structural unit.

11. The photosensitive composition as described in any one of the items7 to 10, wherein the resin (B) has at least one repeating unit selectedfrom 2-alkyl-2-adamantyl(meth)-acrylate anddialkyl(1-adamantyl)methyl(meth)acrylate.

12. The photosensitive composition as described in the item 7, whereinthe resin (B) has a monocyclic or polycyclic alicyclic hydrocarbonstructure.

13. The photosensitive composition as described in the item 12, whereinthe resin (13) has at least one repeating unit selected from2-alkyl-2-adamantyl(meth)acrylate anddialkyl(1-adamantyl)methyl(meth)acrylate, at least one repeating unithaving a lactone structure, and at least one repeating unit having ahydroxyl group.

14. The photosensitive composition as described in the item 12 or 13,wherein the resin (B) further has a repeating unit having a carboxylgroup.

15. The photosensitive composition as described in the item 7, whereinthe resin (B) has a silicon atom in the main or side chain.

16. The photosensitive composition as described in the item 7, whereinthe resin (B) has a repeating unit having a lactone structure.

17. The photosensitive composition as described in any one of the items1 to 16, which further comprises (C) a dissolution inhibiting compoundcapable of decomposing under the action of an acid to increase thesolubility in an alkali developer and having a molecular weight of 3,000or less.

18. The photosensitive composition as described in the item 17, whichfurther comprises (D) a resin soluble in an alkali developer.

19. The photosensitive composition (negative photosensitive composition)as described in any one of the items 1 to 4, which further comprises (D)a resin soluble in an alkali developer, and (E) an acid crosslinkingagent capable of crosslinking with the resin soluble in an alkalideveloper under the action of an acid.

20. The photosensitive composition as described in any one of the items1 to 19, which further comprises at least one of (F) a basic compoundand (G) a fluorine- and/or silicon-containing surfactant.

21. The photosensitive composition as described in the item 20, whereinthe basic compound (F) is a compound having a structure selected from animidazole structure, a diazabicyclo structure, an onium hydroxidestructure, an onium carboxylate structure, a trialkylamine structure, ananiline structure and a pyridine structure, an alkylamine derivativehaving a hydroxyl group and/or an ether bond, or an aniline derivativehaving a hydroxyl group and/or an ether bond.

22. A pattern forming method comprising: forming a resist film from thephotosensitive composition described in any one of the items 1 to 21;and exposing and developing said resist film.

23. An organic acid having a structure represented by the followingformula (I) and a salt thereof:

24. An organic acid represented by the following formula (II) and a saltthereof:HO₃S-A-X-B-R  (II)wherein

A represents a divalent linking group,

X represents a single bond or —SO₂—,

B represents a single bond, an oxygen atom or —N(Rx)-,

Rx represents a hydrogen atom or a monovalent organic group,

R represents a monovalent organic group containing a nitrogen atom, saidnitrogen atom being substituted by the following formula (III):

R′ represents a monovalent organic group, and

when B is —N(Rx)-, R and Rx may combine to form a ring.

25. A sulfonium salt compound of an organic acid represented by thefollowing formula (II) or an iodonium salt compound of an organic acidrepresented by the following formula (II):HO₃S-A-X-B-R  (II)wherein

A represents a divalent linking group,

X represents a single bond or —SO₂—,

B represents a single bond, an oxygen atom or —N(Rx)-,

Rx represents a hydrogen atom or a monovalent organic group,

R represents a monovalent organic group containing a nitrogen atom, saidnitrogen atom being substituted by the following formula (III):

R′ represents a monovalent organic group, and

when B is —N(Rx)-, R and Rx may combine to form a ring.

According to the present invention, a photosensitive compositionexcellent in the sensitivity, resolution and pattern profile, assured oflarge exposure latitude and small pitch dependency, and improved in thesensitivity and dissolution contrast at the exposure with EUV light, apattern forming method using the photosensitive composition, and acompound useful for the photosensitive composition can be provided.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic view of the two-beam interference exposure testingapparatus

Description of Numerical References  1 Laser  2 Diaphragm  3 Shutter  4,5, 6 Reflecting mirrors  7 Condenser lens  8 Prism  9 Immersion solution10 Wafer with antireflection film and resist film 11 Wafer stage

DETAILED DESCRIPTION OF THE INVENTION

The present invention is described in detail below.

In the present invention, when a group (atomic group) is denoted withoutspecifying whether substituted or unsubstituted, the group includes botha group having no substituent and a group having a substituent. Forexample, an “alkyl group”, includes not only an alkyl group having nosubstituent (unsubstituted alkyl group) but also an alkyl group having asubstituent (substituted alkyl group).

The positive photosensitive composition, preferably positive resistcomposition, of the present invention comprises (A) a compound capableof generating an organic acid represented by formula (I) uponirradiation with actinic rays or radiation and (B) a resin capable ofdecomposing under the action of an acid to increase the solubility in analkali developer and if desired, further comprises (C) a dissolutioninhibiting compound capable of decomposing under the action of an acidto increase the solubility in an alkali developer and having a molecularweight of 3,000 or less. Alternatively, the positive photosensitivecomposition comprises (A) a compound capable of generating an organicacid represented by formula (I) upon irradiation with actinic rays orradiation, (D) a resin soluble in an alkali developer and (C) adissolution inhibiting compound capable of decomposing under the actionof an acid to increase the solubility in an alkali developer and havinga molecular weight of 3,000 or less.

The negative photosensitive composition, preferably negative resistcomposition, of the present invention comprises (A) a compound capableof generating an organic acid represented by formula (I) uponirradiation with actinic rays or radiation, (D) a resin soluble in analkali developer and (E) an acid crosslinking agent capable ofcrosslinking with the alkali developer-soluble resin under the action ofan acid.

(A) Compound Capable of Generating an Organic Acid Having a Bond whichis Cleaved by an Acid, Upon Irradiation with Actinic Rays or Radiation

The photosensitive composition of the present invention comprises (A) acompound capable of generating an organic acid having a bond which iscleaved by an acid, upon irradiation with actinic rays or radiation.

The compound (A) generates an organic acid by receiving actinic rays orradiation from, for example, an excimer laser such as KrF and ArF. Thisorganic acid has, within the molecule, a bond which is cleaved by anacid. At this time, the acid for decomposing the organic acid may be theorganic acid itself generated from the compound (A) or may be otheracid. The other acid includes (A′) a compound capable of generating anacid compound other than that described above. By using such a compound(A) in the photosensitive composition, the resolution is enhanced.

Examples of the bond which is contained in the organic acid generatedfrom the compound (A) and which is cleaved by the effect of an acidinclude an amide bond, an ester bond, an acetal bond, a carbamoyl bondand a carbonate bond.

The structure having such a bond which is cleaved by an acid ispreferably a carbamoyl structure represented by the following formula(I):

The organic acid generated from the compound (A) is more preferably anorganic acid represented by the following formula (II). By applying sucha compound to the photosensitive composition, the exposure latitude,pattern profile and pitch dependency are improved.HO₃S-A-X-B-R  (II)

In formula (II),

A represents a divalent linking group,

X represents a single bond or —SO₂—,

B represents a single bond, an oxygen atom or —N(Rx)-,

Rx represents a hydrogen atom or a monovalent organic group,

R represents a monovalent organic group containing a nitrogen atom, thenitrogen atom being substituted by the following formula (III):

R′ represents a monovalent organic group, and

when B is —N(Rx)-, R and Rx may combine to form a ring.

The divalent linking group as A is preferably a divalent organic grouphaving a carbon number of 1 to 8, and examples thereof include analkylene group and a phenylene group. The divalent linking group as A ismore preferably an alkylene group (preferably having a carbon number of2 to 6, more preferably from 2 to 4). The alkylene group may contain, inthe alkylene chain, a linking group such as oxygen atom and sulfur atom.The alkylene group may be substituted by a fluorine atom and in thiscase, the alkylene group is preferably an alkylene group where from 30to 100% by number of the hydrogen atom is replaced by a fluorine atom,more preferably an alkylene group where the carbon atom bonded to theHO₃S— site has a fluorine atom, still more preferably aperfluoroalkylene group, and most preferably a perfluoroethylene group,a perfluoropropylene group or a perfluorobutylene group, because thesensitivity is enhanced.

The monovalent organic group as Rx and Rx′ is preferably a monovalentorganic group having a carbon number of 4 to 20, and examples thereofinclude an alkyl group, a cycloalkyl group, an aryl group, an aralkylgroup and an alkenyl group.

The alkyl group as Rx, which may have a substituent, is preferably alinear or branched alkyl group having a carbon number of 1 to 20 and maycontain, in the alkyl chain, an oxygen atom, a sulfur atom or a nitrogenatom. Specific examples thereof include a linear alkyl group such asmethyl group, ethyl group, n-propyl group, n-butyl group, n-pentylgroup, n-hexyl group, n-octyl group, n-dodecyl group, n-tetradecyl groupand n-octadecyl group; and a branched alkyl group such as isopropylgroup, isobutyl group, tert-butyl group, neopentyl group and2-ethylhexyl group.

The alkyl group having a substituent particularly includes a group wherea cycloalkyl group is substituted to a linear or branched alkyl group,such as adamantylmethyl group, adamantylethyl group, cyclohexylethylgroup and camphor residue.

The cycloalkyl group as Rx, which may have a substituent, is preferablya cycloalkyl group having a carbon number of 3 to 20 and may contain, inthe ring, an oxygen atom. Specific examples thereof include acyclopropyl group, a cyclopentyl group, a cyclohexyl group, a norbornylgroup and an adamantyl group.

The aryl group as Rx, which may have a substituent, is preferably anaryl group having a carbon number of 6 to 14, and examples thereofinclude a phenyl group and a naphthyl group.

The aralkyl group as Rx is preferably an aralkyl group having a carbonnumber of 7 to 20, and examples thereof include a benzyl group, aphenethyl group, a naphthylmethyl group and a naphthylethyl group.

The alkenyl group as Rx includes a group having a double bond at anarbitrary position of the alkyl group described for Rx.

R is a monovalent organic group containing at least one nitrogen atom,the nitrogen atom being substituted by a substituent of formula (M), andthe monovalent organic group as R preferably has a carbon number of 5 to20. Examples thereof include an alkyl group, a cycloalkyl group, an arylgroup, an aralkyl group and an alkenyl group, each having a nitrogenatom substituted by formula (III), and these are the same as thosedescribed for Rx.

R′ is a monovalent organic group preferably having a carbon number of 4to 15, and examples thereof include an alkyl group, a cycloalkyl group,an aryl group, an aralkyl group and an alkenyl group. These are the sameas those described for Rx. In particular, R′ is preferably an alkylgroup or an aralkyl group.

The organic acid having a structure represented by formula (I), theorganic acid represented by formula (II) and salts thereof are novelcompounds.

The organic acid of the present invention can be synthesized by using ageneral sulfonic acid esterification reaction or sulfonamidationreaction. For example, in the case of an organic acid having a structurerepresented by formula (I), a method of selectively reacting onesulfonyl halide moiety of a bis-sulfonyl halide compound with an amine,alcohol or the like containing a partial structure represented byformula (I) to form a sulfonamide bond or a sulfonic acid ester bond,and then hydrolyzing the other sulfonyl halide moiety, or a method ofring-opening a cyclic sulfonic anhydride by an amine or alcoholcontaining a partial structure represented by formula (I) may be used.The amine or alcohol containing a partial structure represented byformula (I) can be synthesized by reacting an amine or alcohol with ananhydride (e.g., (R′O₂C)₂O, R′O₂CCl) or an acid chloride compound underbasic condition.

Specific preferred examples of the organic acid of the presentinvention, namely, the organic acid being generated by the irradiationof actinic rays or radiation on the compound (A) and having a bond whichis cleaved by an acid, are set forth below, but the present invention isnot limited thereto.

The compound (A) is preferably a sulfonium salt compound or iodoniumsalt compound of an organic acid having a bond which is cleaved by anacid, more preferably a compound represented by the following formula(A1) or (A2):

In formula (A1), R₂₀₁, R₂₀₂ and R₂₀₃ each independently represents anorganic group.

X⁻ represents an anion of an organic acid having a bond which is cleavedby an acid.

The carbon number of the organic group as R₂₀₁, R₂₀₂ and R₂₀₃ isgenerally from 1 to 30, preferably from 1 to 20.

Two members out of R₂₀₁ to R₂₀₃ may combine to form a ring structure andthe ring may contain an oxygen atom, a sulfur atom, an ester bond, anamide bond or a carbonyl group. Examples of the group formed bycombining two members out of R₂₀₁ to R₂₀₃ include an alkylene group(e.g., butylene, pentylene).

Specific examples of the organic group as R₂₀₁, R₂₀₂ and R₂₀₃ includethe corresponding groups in the compounds (A1a), (A1b) and (A1c)described later.

The compound may be a compound having a plurality of structuresrepresented by formula (A1). For example, the compound may be a compoundhaving a structure that at least one of R₂₀₁ to R₂₀₃ in the compoundrepresented by formula (A1) is bonded to at least one of R₂₀₁ to R₂₀₃ inanother compound represented by formula (A1).

The component (A1) is more preferably a compound (A1a), (A1b) or (A1c)described below.

The compound (A1a) is an arylsulfonium compound where at least one ofR₂₀₁ to R₂₀₃ in formula (A1) is an aryl group, that is, a compoundhaving arylsulfonium as the cation.

In the arylsulfonium compound, R₂₀₁ to R₂₀₃ all may be an aryl group ora part of R₂₀₁ to R₂₀₃ may be an aryl group with the remaining being analkyl group or a cycloalkyl group.

Examples of the arylsulfonium compound include, a triarylsulfoniumcompound, a diarylalkylsulfonium compound, a diarylcycloakylsulfoniumcompound, an aryldialkylsulfonium compound, an aryldicycloalkylsulfoniumcompound and an arylalkylcycloalkylsulfonium compound.

The aryl group in the arylsulfonium compound is preferably a phenylgroup or a naphthyl group, more preferably a phenyl group. In the casewhere the arylsulfonium compound has two or more aryl groups, these twoor more aryl groups may be the same of different.

The alkyl group which is present, if desired, in the arylsulfoniumcompound is preferably a linear or branched alkyl group having a carbonnumber of 1 to 15, such as methyl group, ethyl group, propyl group,n-butyl group, sec-butyl group and tert-butyl group.

The cycloalkyl group which is present, if desired, in the arylsulfoniumcompound is preferably a cycloalkyl group having a carbon number of 3 to15, such as cyclopropyl group, cyclobutyl group and cyclohexyl group.

The aryl group, alkyl group and cycloalkyl group of R₂₀₁ to R₂₀₃ eachmay have, as the substituent, an alkyl group (for example, an alkylgroup having a carbon number of 1 to 0.15), a cycloalkyl group (forexample, a cycloalkyl group having a carbon number of 3 to 15), an arylgroup (for example, an aryl group having a carbon number of 6 to 14), analkoxy group (for example, an alkoxy group having a carbon number of 1to 15), a halogen atom, a hydroxyl group or a phenylthio group. Thesubstituent is preferably a linear or branched alkyl group having acarbon number of 1 to 12, a cycloalkyl group having a carbon number of 3to 12, or a linear, branched or cyclic alkoxy group having a carbonnumber of 1 to 12, and most preferably an alkyl group having a carbonnumber of 1 to 4, or an alkoxy group having a carbon number of 1 to 4.The substituent may be substituted to any one of three members R₂₀₁ toR₂₀₃ or may be substituted to all of these three members. In the casewhere R₂₀₁ to R₂₀₃ are an aryl group, the substituent is preferablysubstituted at the p-position of the aryl group.

The compound (A1b) is described below.

The compound (A1b) is a compound when R₂₀₁ to R₂₀₃ in formula (A1) eachindependently represents an organic group not containing an aromaticring. The aromatic ring as used herein includes an aromatic ring havinga heteroatom.

The organic group as R₂₀₁ to R₂₀₃ not containing an aromatic ring has acarbon number of generally from 1 to 30, preferably from 1 to 20.

R₂₀₁ to R₂₀₃ each independently represents preferably an alkyl group, acycloalkyl group, an allyl group or a vinyl group, more preferably alinear or branched 2-oxoalkyl group, a 2-oxocycloalkyl group or analkoxycarbonylmethyl group, still more preferably a linear or branched2-oxoalkyl group.

The alkyl group as R₂₀₁ to R₂₀₃ may be either linear or branched and ispreferably a linear or branched alkyl group having a carbon number of 1to 20 (e.g., methyl, ethyl, propyl, butyl, pentyl), more preferably alinear or branched 2-oxoalkyl group or an alkoxycarbonylmethyl group.

The cycloalkyl group as R₂₀₀ to R₂₀₃ is preferably a cycloalkyl grouphaving a carbon number of 3 to 10 (e.g., cyclopentyl, cyclohexyl,norbornyl), more preferably a 2-oxocycloalkyl group.

The linear or branched 2-oxoalkyl group as R₂₀₁ to R₂₀₃ may have adouble bond in the chain, and preferred examples thereof include a grouphaving >C═O at the 2-position of the above-described alkyl group.

The 2-oxocycloalkyl group as R₂₀₁ to R₂₀₃ may have a double bond in thechain, and preferred examples thereof include a group having >C═O at the2-position of the above-described cycloalkyl group.

Preferred examples of the alkoxy group in the alkoxycarbonylmethyl groupas R₂₀₁ to R₂₀₃ include an alkyl group having a carbon number of 1 to 5(e.g., methoxy, ethoxy, propoxy, butoxy, pentoxy).

R₂₀₁ to R₂₀₃ each may be further substituted by a halogen atom, analkoxy group (for example, an alkoxy group having a carbon number of 1to 5), an alkoxycarbonyl group (for example, an alkoxycarbonyl grouphaving a carbon number of 1 to 5), a hydroxyl group, a cyano group or anitro group.

The compound (A1c) is a compound represented by the following formula(A1c), and this is a compound having an arylacylsulfonium saltstructure.

In formula (A1c), R₂₁₃ represents an aryl group which may besubstituted, and is preferably a phenyl group or a naphthyl group.

Preferred examples of the substituent on R₂₁₃ include an alkyl group, analkoxy group, an acyl group, a nitro group, a hydroxyl group, analkoxycarbonyl group and a carboxy group.

R₂₁₄ and R₂₁₅ each independently represents a hydrogen atom, an alkylgroup or a cycloalkyl group.

Y₂₀₁ and Y₂₀₂ each independently represents an alkyl group, a cycloalkylgroup, an aryl group or a vinyl group.

X⁻ represents an anion of an organic acid having a bond which is cleavedby an acid.

R₂₁₃ and R₂₁₄ may combine with each other to form a ring structure, R₂₁₄and R₂₁₅ may combine with each other to form a ring structure, and Y₂₀₁and Y₂₀₂ may combine with each other to form a ring structure. The ringstructure formed may contain an oxygen atom, a sulfur atom, an esterbond or an amide bond. Examples of the group formed by combining eachpair of R₂₁₃ and R₂₁₄, R₂₁₄ and R₂₁₅, or Y₂₀₁ and Y₂₀₂ include abutylene group and a pentylene group.

The alkyl group as R₂₁₄, R₂₁₅, Y₂₀₁ and Y₂₀₂ is preferably a linear orbranched alkyl group having a carbon number of 1 to 20. The alkyl groupas Y₂₀₀ and Y₂₀₂ is more preferably a 2-oxoalkyl group having >C═O atthe 2 position of the alkyl group, an alkoxycarbonylalkyl group(preferably with the alkoxy group having a carbon number of 2 to 20), ora carboxyalkyl group.

The cycloalkyl group as R₂₁₄, R₂₁₅, Y₂₀₁ and Y₂₀₂ is preferably acycloalkyl group having a carbon number of 3 to 20.

Y₂₀₁ and Y₂₀₂ each is preferably an alkyl group having a carbon numberof 4 or more, more preferably from 4 to 6, still more preferably from 4to 12.

At least either one of R₂₁₄ and R₂₁₅ is preferably an alkyl group, andmore preferably, R₂₁₄ and R₂₁₅ both are an alkyl group.

In formula (A2), R₂₀₄ and R₂₀₅ each independently represents an arylgroup, an alkyl group or a cycloalkyl group.

X⁻ represents an anion of an organic acid having a bond which is cleavedby an acid.

The aryl group of R₂₀₄ and R₂₀₅ is preferably a phenyl group or anaphthyl group, more preferably a phenyl group.

The alkyl group as R₂₀₄ and R₂₀₅ may be either linear or branched and ispreferably a linear or branched alkyl group having a carbon number of 1to 10 (e.g., methyl, ethyl, propyl, butyl, pentyl).

The cycloalkyl group as R₂₀₄ and R₂₀₅ is preferably a cycloalkyl grouphaving a carbon number of 3 to 10 (e.g., cyclopentyl, cyclohexyl,norbornyl).

R₂₀₄ and R₂₀₅ may have a substituent, and examples of the substituentwhich R₂₀₄ and R₂₀₅ may have include an alkyl group (for example, analkyl group having a carbon number of 1 to 15), a cycloalkyl group (forexample, a cycloalkyl group having a carbon number of 3 to 15), an arylgroup (for example, an aryl group having a carbon number of 6 to 15), analkoxy group (for example, an alkoxy group having a carbon number of 1to 15), a halogen atom, a hydroxyl group and a phenylthio group.

The compound (A) is preferably a compound represented by formula (A1),more preferably a compound represented by any one of formulae (A1) to(A1c).

Specific examples of the compound (A) are set forth below, but thepresent invention is not limited thereto.

The sulfonic salt compound and iodonium salt compound of the organicacid represented by formula (I) or (II) are novel compounds.

The compound (A) can be easily synthesized from the organic acid of thepresent invention or a lithium, sodium or potassium salt thereof and ahydroxide, bromide, chloride or the like of iodonium or sulfonium, byutilizing the salt-exchange method described in JP-T-11-501909 orJP-A-2003-246786.

The content of the compound (A) in the photosensitive composition of thepresent invention is preferably from 0.1 to 20 mass %, more preferablyfrom 0.5 to 10 mass %, still more preferably from 1 to 7 mass %, basedon the solid content of the composition.

(Acid Generator Used in Combination)

In the present invention, a compound (acid generator) capable ofgenerating an acid upon irradiation with actinic rays or radiation mayalso be used in addition to the compound (A).

The amount added of the acid generator which can be used in combinationis, in terms of the molar ratio (compound (A)/another acid generator),usually from 90/10 to 5/95, preferably from 60/40 to 5/95, morepreferably from 50/50 to 5/95.

This photo-acid generator which can be used in combination may beappropriately selected from a photoinitiator for photocationicpolymerization, a photoinitiator for photoradical polymerization, aphoto-decoloring agent for dyes, a photo-discoloring agent, a knowncompound capable of generating an acid upon irradiation with actinicrays or radiation, which is used for microresist and the like, and amixture thereof.

Examples thereof include diazonium salt, phosphonium salt, sulfoniumsalt, iodonium salt, imidosulfonate, oxime sulfonate, diazodisulfone,disulfone and o-nitrobenzyl sulfonate.

Also, a compound where the above-described group or compound capable ofgenerating an acid upon irradiation with actinic rays or radiation isintroduced into the polymer main or side chain, such as compoundsdescribed in U.S. Pat. No. 3,849,137, German Patent 3,914,407,JP-A-63-26653, JP-A-55-164824, JP-A-62-69263, JP-A-63-146038,JP-A-63-163452, JP-A-62-153853 and JP-A-63-146029, may be used.

Furthermore, a compound capable of generating an acid by the effect oflight described, for example, in U.S. Pat. No. 3,779,778 and EuropeanPatent 126,712 may also be used.

Among the compounds capable of decomposing upon irradiation with actinicrays or radiation to generate an acid, which can be used in combination,preferred are the compounds represented by the following formulae (ZI),(ZII) and (ZIII):

In formula (ZI), R₂₀₁, R₂₀₂ and R₂₀₃ each independently represents anorganic group.

The number of carbons in the organic group as R₂₀₁, R₂₀₂ and R₂₀₃ isgenerally from 1 to 30, preferably from 1 to 20.

Two members out of R₂₀₁ to R₂₀₃ may combine to form a ring structure,and the ring may contain an oxygen atom, a sulfur atom, an ester bond,an amide bond or a carbonyl group. Examples of the group formed bycombining two members out of R₂₀₁ to R₂₀₃ include an alkylene group(e.g., butylene, pentylene).

Z⁻ represents a non-nucleophilic anion.

Examples of the non-nucleophilic anion represented by Z⁻ includesulfonate anion, carboxylate anion, sulfonylimide anion,bis(alkylsulfonyl)imide anion and tris(alkylsulfonyl)methyl anion.

The non-nucleophilic anion is an anion having an extremely low abilityof causing a nucleophilic reaction and this anion can prevent thedecomposition in aging due to intramolecular nucleophilic reaction. Bythis anion, the aging stability of resist is enhanced.

Examples of the sulfonate anion include aliphatic sulfonate anion,aromatic sulfonate anion and camphorsulfonate anion.

Examples of the carboxylate anion include aliphatic carboxylate anion,aromatic carboxylate anion and aralkylcarboxylate anion.

The aliphatic moiety in the aliphatic sulfonate anion may be an alkylgroup or a cycloalkyl group but is preferably an alkyl group having from1 to 30 carbon atoms or a cycloalkyl group having from 3 to 30 carbonatoms, such as methyl group, ethyl group, propyl group, isopropyl group,n-butyl group, isobutyl group, sec-butyl group, pentyl group, neopentylgroup, hexyl group, heptyl group, octyl group, nonyl group, decyl group,undecyl group, dodecyl group, tridecyl group, tetradecyl group,pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group,nonadecyl group, eicosyl group, cyclopropyl group, cyclopentyl group,cyclohexyl group, adamantyl group, norbornyl group and boronyl group.

The aromatic group in the aromatic sulfonate anion is preferably an arylgroup having a carbon number of 6 to 14, such as phenyl group, tolylgroup and naphthyl group.

The alkyl group, cycloalkyl group and aryl group in the aliphaticsulfonate anion and aromatic sulfonate anion each may have asubstituent. Examples of the substituent for the alkyl group, cycloalkylgroup and aryl group in the aliphatic sulfonate anion and aromaticsulfonate anion include a nitro group, a halogen atom (e.g., fluorine,chlorine, bromine, iodine), a carboxyl group, a hydroxyl group, an aminogroup, a cyano group, an alkoxy group (preferably having a carbon numberof 1 to 5), a cycloalkyl group (preferably having a carbon number of 3to 15), an aryl group (preferably having a carbon number of 6 to 14), analkoxycarbonyl group (preferably having a carbon number of 2 to 7), anacyl group (preferably having a carbon number of 2 to 12) and analkoxycarbonyloxy group (preferably having a carbon number of 2 to 7).As for the aryl group and ring structure in each group, examples of thesubstituent further include an alkyl group (preferably having a carbonnumber of 1 to 15).

Examples of the aliphatic moiety in the aliphatic carboxylate anioninclude the same alkyl group and cycloalkyl group as in the aliphaticsulfonate anion.

Examples of the aromatic group in the aromatic carboxylate anion includethe same aryl group as in the aromatic sulfonate anion.

The aralkyl group in the aralkylcarboxylate anion is preferably anaralkyl group having a carbon number of 6 to 12, such as benzyl group,phenethyl group, naphthylmethyl group, naphthylethyl group andnaphthylmethyl group.

The alkyl group, cycloalkyl group, aryl group and aralkyl group in thealiphatic carboxylate anion, aromatic carboxylate anion andaralkylcarboxylate anion each may have a substituent. Examples of thesubstituent for the alkyl group, cycloalkyl group, aryl group andaralkyl group in the aliphatic carboxylate anion, aromatic carboxylateanion and aralkylcarboxylate-anion include the same halogen atom, alkylgroup, cycloalkyl group, alkoxy group and alkylthio group as in thearomatic sulfonate anion.

Examples of the sulfonylimide anion include saccharin anion.

The alkyl group in the bis(alkylsulfonyl)imide anion andtris(alkylsulfonyl)methyl anion is preferably an alkyl group having acarbon number of 1 to 5, such as methyl group, ethyl group, propylgroup, isopropyl group, n-butyl group, isobutyl group, sec-butyl group,pentyl group and neopentyl group. Examples of the substituent for suchan alkyl group include a halogen atom, a halogen atom-substituted alkyl‘group,’ an alkoxy group and an alkylthio group. Among these, an alkylgroup substituted by a fluorine atom is preferred.

Other examples of the non-nucleophilic anion include fluorinatedphosphorus, fluorinated boron and fluorinated antimony.

The non-nucleophilic anion of Z⁻ is preferably an aliphatic sulfonateanion with the α-position of sulfonic acid being substituted by afluorine atom, an aromatic sulfonate anion substituted by a fluorineatom or a group having a fluorine atom, a bis(alkylsulfonyl)imide anionwith the alkyl group being substituted by a fluorine atom, or atris(alkylsulfonyl)methide anion with the alkyl group being substitutedby a fluorine atom, more preferably a perfluoroaliphatic sulfonate anionhaving a carbon number of 4 to 8 or a benzenesulfonate anion having afluorine atom, still more preferably nonafluorobutanesulfonate anion,perfluorooctanesulfonate anion, pentafluorobenzenesulfonate anion or3,5-bis(trifluoromethyl)benzenesulfonate anion.

Examples of the organic group as R₂₀₁, R₂₀₂ and R₂₀₃ includecorresponding groups in the compounds (ZI-1), (ZI-2) and (ZI-3) whichare described later.

The compound may be a compound having a plurality of structuresrepresented by formula (Z1), for example, a compound having a structurethat at least one of R₂₀₁ to R₂₀₃ in the compound represented by formula(Z1) is bonded to at least one of R₂₀₁ to R₂₀₃ in another compoundrepresented by formula (Z1).

The component (Z1) is more preferably a compound (ZI-1), (ZI-2) or(ZI-3) described below.

The compound (ZI-1) is an arylsulfonium compound where at least one ofR₂₀₁ to R₂₀₃ in formula (Z1) is an aryl group, that is, a compoundhaving an arylsulfonium as the cation.

In the arylsulfonium compound, R₂₀₁ to R₂₀₃ all may be an aryl group ora part of R₂₀₁ to R₂₀₃ may be an aryl group with the remaining being analkyl group or a cycloalkyl group.

Examples of the arylsulfonium compound include a triarylsulfoniumcompound, a diarylalkylsulfonium compound, an aryldialkylsulfoniumcompound, a diarylcycloalkylsulfonium compound and anaryldicycloalkylsulfonium compound.

The aryl group in the arylsulfonium compound is preferably a phenylgroup or a naphthyl group, more preferably a phenyl group. In the casewhere the arylsulfonium compound has two or more aryl groups, these twoor more aryl groups may be the same of different.

The alkyl group or cycloalkyl group which is present, if desired, in thearylsulfonium compound is preferably a linear or branched alkyl grouphaving a carbon number of 1 to 15 or a cycloalkyl group having a carbonnumber of 3 to 15, such as methyl group, ethyl group, propyl group,n-butyl group, sec-butyl group, tert-butyl group, cyclopropyl group,cyclobutyl group and cyclohexyl group.

The aryl group, alkyl group and cycloalkyl group of R₂₀₁ to R₂₀₃ eachmay have, as the substituent, an alkyl group (for example, an alkylgroup having a carbon number of 1 to 15), a cycloalkyl group (forexample, a cycloalkyl group having a carbon number of 3 to 15), an arylgroup (for example, an aryl group having a carbon number of 6 to 14), analkoxy group (for example, an alkoxy group having a carbon number of 1to 15), a halogen atom, a hydroxyl group or a phenylthio group. Thesubstituent is preferably a linear or branched alkyl group having acarbon number of 1 to 12, a cycloalkyl group having a carbon number of 3to 12, or a linear, branched or cyclic alkoxy group having a carbonnumber of 1 to 12, more preferably an alkyl group having a carbon numberof 1 to 4, or an alkoxy group having a carbon number of 1 to 4. Thesubstituent may be substituted to any one of three members R₂₀₁ to R₂₀₃or may be substituted to all of these three members. In the case whereR₂₀₁ to R₂₀₃ each is an aryl group, the substituent is preferablysubstituted at the p-position of the aryl group.

The compound (ZI-2) is described below.

The compound (ZI-2) is a compound where R₂₀₁ to R₂₀₃ in formula (ZI)each independently represents an aromatic ring-free organic group. Thearomatic ring as used herein includes an aromatic ring containing aheteroatom.

The aromatic ring-free organic group as R₂₀₁ to R₂₀₃ generally has acarbon number of 1 to 30, preferably from 1 to 20.

R₂₀₁ to R₂₀₃ each independently represents preferably an alkyl group, acycloalkyl group, an allyl group or a vinyl group, more preferably alinear or branched 2-oxoalkyl group, a 2-oxocycloalkyl group or analkoxycarbonylmethyl group, and most preferably a linear or branched2-oxoalkyl group.

The alkyl group and cycloalkyl group of R₂₀₁ to R₂₀₃ are preferably alinear or branched alkyl group having a carbon number of 1 to 10 (e.g.,methyl, ethyl, propyl, butyl, pentyl) and a cycloalkyl group having acarbon number of 3 to 10 (e.g., cyclopentyl, cyclohexyl, norbornyl). Thealkyl group is more preferably a 2-oxoalkyl group or analkoxycarbonylmethyl group. The cycloalkyl group is more preferably a2-oxocycloalkyl group.

The 2-oxoalkyl group may be either linear or branched and is preferablya group having >C═O at the 2-position of the above-described alkylgroup.

The 2-oxocycloalkyl group is preferably a group having >C═O at the2-position of the above-described cycloalkyl group.

The alkoxy group in the alkoxycarbonylmethyl group is preferably analkyl group having a carbon number of 1 to 5 (e.g., methoxy, ethoxy,propoxy, butoxy, pentyloxy).

R₂₀₁ to R₂₀₃ each may be further substituted by a halogen atom, analkoxy group (for example, an alkoxy group having a carbon number of 1to 5), a hydroxyl group, a cyano group or a nitro group.

The compound (ZI-3) is a compound represented by the following formula(ZI-3), and this is a compound having a phenacylsulfonium saltstructure.

In formula (ZI-3), R_(1c) to R_(5c) each independently represents ahydrogen atom, an alkyl group, a cycloalkyl group, an alkoxy group or ahalogen atom.

R_(6c) and R_(7c) each independently represents a hydrogen atom, analkyl group or a cycloalkyl group.

R_(x) and R_(y) each independently represents an alkyl group, acycloalkyl group, an allyl group or a vinyl group.

Any two or more members out of R_(1c) to R_(5c) or each pair of R_(6c)and R_(7c), and R_(x) and R_(y) may combine with each other to form aring structure, and the ring structure may contain an oxygen atom, asulfur atom, an ester bond or an amide bond. Examples of the groupformed by combining any two or more members out of R_(1c) to R_(5c) orcombining each pair of R_(6c) and R_(7c), and R_(x) and R_(y) include abutylene group and a pentylene group.

Zc⁻ represents a non-nucleophilic anion, and examples thereof are thesame as those of the non-nucleophilic anion of Z⁻ in formula (ZI).

The alkyl group as R_(1c) to R_(7c) may be either linear or branched andthis is, for example, an alkyl group having a carbon number of 1 to 20,preferably a linear or branched alkyl group having a carbon number of 1to 12 (e.g., methyl, ethyl, linear or branched propyl, linear orbranched butyl, linear or branched pentyl), and the cycloalkyl group is,for example, a cycloalkyl group having a carbon number of 3 to 8 (e.g.,cyclopentyl, cyclohexyl).

The alkoxy group as R_(1c) to R_(5c) may be linear, branched or cyclicand this is, for example, an alkoxy group having a carbon number of 1 to10, preferably a linear or branched alkoxy group having a carbon numberof 1 to 5 (e.g., methoxy, ethoxy, linear or branched propoxy, linear orbranched butoxy, linear or branched pentoxy) or a cyclic alkoxy grouphaving a carbon number of 3 to 8 (e.g., cyclopentyloxy, cyclohexyloxy).

A compound where any one of R_(1c) to R_(5c) is a linear or branchedalkyl group, a cycloalkyl group or a linear, branched or cyclic alkoxygroup is preferred, and a compound where the sum of carbon atoms ofR_(1c) to R_(5c) is from 2 to 15 is more preferred. In this case, thesolubility in solvent is more enhanced and the generation of particlesduring storage is suppressed.

Examples of the alkyl group and cycloalkyl group as R_(x) and R_(y)include the same alkyl group and cycloalkyl group as in R_(1c) toR_(7c). Among these, a 2-oxoalkyl group, a 2-oxocycloalkyl group and analkoxycarbonylmethyl group are preferred.

Examples of the 2-oxoalkyl group and 2-oxocycloalkyl group include agroup having >C═O at the 2-position of the alkyl group or cycloalkylgroup as R_(1c) to R_(7c).

Examples of the alkoxy group in the alkoxycarbonylmethyl group includethe same alkoxy group as in R_(1c) to R_(5c).

R_(x) and R_(y) each is preferably an alkyl or cycloalkyl group having acarbon number of 4 or more, more preferably 6 or more, still morepreferably 8 or more.

In formulae (ZII) and (ZIII), R₂₀₄ to R₂₀₇ each independently representsan aryl group, an alkyl group or a cycloalkyl group.

The aryl group as R₂₀₄ to R₂₀₇ is preferably a phenyl group or anaphthyl group, more preferably a phenyl group.

The alkyl group and cycloalkyl group in R₂₀₄ to R₂₀₇ are preferably alinear or branched alkyl group having a carbon number of 1 to 10 (e.g.,methyl, ethyl, propyl, butyl, pentyl) and a cycloalkyl group having acarbon number of 3 to 10 (e.g., cyclopentyl, cyclohexyl, norbornyl).

The aryl group, alkyl group and cycloalkyl group of R₂₀₄ to R₂₀₇ mayhave a substituent. Examples of the substituent which the aryl group,alkyl group and cycloalkyl group of R₂₀₄ to R₂₀₇ may have include analkyl group (for example, an alkyl group having a carbon number of 1 to15), a cycloalkyl group (for example, a cycloalkyl group having a carbonnumber of 3 to 15), an aryl group (for example, an aryl group having acarbon number of 6 to 15), an alkoxy group (for example, an alkoxy grouphaving a carbon number of 1 to 15), a halogen atom, a hydroxyl group anda phenylthio group.

Z⁻ represents a non-nucleophilic anion and examples thereof include thesame as those of the non-nucleophilic anion of Z⁻ in formula (ZI).

Other examples of the compound capable of decomposing upon irradiationwith actinic rays or radiation to generate an acid, which can be used incombination, include the compounds represented by the following formulae(ZIV), (ZV) and (ZVI):

In formulae (ZIV) to (ZVI),

Ar₃ and Ar₄ each independently represents an aryl group,

R₂₀₆, R₂₀₇ and R₂₀₈ each independently represents an alkyl group, acycloalkyl group or an aryl group, and

A represents an alkylene group, an alkenylene group or an arylene group.

Among the compounds capable of decomposing upon irradiation with actinicrays or radiation to generate an acid, which can be used in combination,more preferred are the compounds represented by formulae (ZI) to (ZIII).

The compound of decomposing upon irradiation with actinic rays orradiation to generate an acid, which can be used in combination, ispreferably a compound capable of generating an acid having one sulfonicacid group or imide group, more preferably a compound capable ofgenerating a monovalent perfluoroalkanesulfonic acid, a compound capableof generating an aromatic sulfonic acid substituted by a fluorine atomor fluorine atom-containing group, or a compound capable of generatingan imide acid substituted by a monovalent fluorine atom or fluorineatom-containing group. The acid generated by the acid generator usablein combination is most preferably a fluorinated substitutedalkanesulfonic acid, fluorinated substituted benzenesulfonic acid orfluorinated substituted imide acid having a pKa of −1 or less, and inthis case, the sensitivity is enhanced.

Particularly preferred examples of the compound capable of decomposingupon irradiation with actinic rays or radiation to generate an acid,which can be used in combination, are set forth below.

[2] (B) Resin Capable of Decomposing Under the Action of an Acid toIncrease the Solubility in an Alkali Developer (Hereinafter SometimesReferred to as a “Component (B)”)

The resin capable of decomposing under the action of an acid to increasethe solubility in an alkali developer, which is used in the positivephotosensitive composition of the present invention, is a resin having,in ether one or both of the main chain and the side chain thereof, agroup capable of decomposing under the action of an acid (hereinaftersometimes referred to as an “acid-decomposable group”). Of these, aresin having an acid-decomposable group in the side chain is preferred.

The group capable of decomposing under the action of an acid ispreferably a group resulting from replacement of the hydrogen atom of a—COOH or —OH group with a group which splits off by the effect of anacid.

In the present invention, the acid-decomposable group is preferably anacetal group or a tertiary ester group.

In the case where the group capable of decomposing under the action ofan acid is bonded as a side chain, the mother resin is an alkali-solubleresin having an —OH or —COOH group in the side chain. Examples thereofinclude an alkali-soluble resin described later.

The alkali dissolution rate of the alkali-soluble resin is preferably170 A/sec or more, more preferably 330 A/sec or more (A is angstrom), asmeasured (at 23° C.) in 0.261N tetramethylammonium hydroxide (TMAH).

From this standpoint, the alkali-soluble resin is preferably analkali-soluble resin having a hydroxystyrene structure unit, such as o-,m- or p-poly(hydroxystyrene) or copolymer thereof, hydrogenatedpoly(hydroxystyrene), halogen- or alkyl-substitutedpoly(hydroxystyrene), partially O-alkylated or O-acylatedpoly(hydroxystyrene), styrene-hydroxystyrene copolymer,α-methylstyrene-hydroxystyrene copolymer and hydrogenated novolak resin;or an alkali-soluble resin containing a repeating unit having a carboxylgroup, such as (meth)acrylic acid and norbornene carboxylic acid.

Preferred examples of the repeating unit having an acid-decomposablegroup for use in the present invention includetert-butoxycarbonyloxystyrene, 1-alkoxyethoxystyrene and tertiaryalkyl(meth)acrylate. Among these, 2-alkyl-2-adamantyl(meth)acrylate anddialkyl(1-adamantyl)methyl(meth)acrylate are preferred.

The component (B) for use in the present invention can be obtained byreacting an acid-decomposable group precursor with an alkali-solubleresin or copolymerizing an acid-decomposable group-bonded alkali-solubleresin monomer with various monomers, and this is disclosed in EuropeanPatent 254853, JP-A-2-25850, JP-A-3-223860 and JP-A-4-251259.

In the case of irradiation the positive photosensitive composition ofthe present invention with KrF excimer laser light, electron beam, X-rayor high-energy light at a wavelength of 50 nm or less (e.g., EUV), theresin as the component (B) preferably has a hydroxystyrene repeatingunit, and the resin is more preferably a copolymer ofhydroxystyrene/hydroxystyrene protected by an acid-decomposable group,or a tertiary alkyl ester of hydroxystyrene/methacrylic acid.

Specific examples of the component (B) for use in the present inventionare set forth below, but the present invention is not limited thereto.

In these specific examples, “tBu” indicates a tert-butyl group.

The content of the group capable of decomposing under the action of anacid is expressed by B/(B+S) using the number (B) of acid-decomposablegroups in the resin and the number (S) of alkali-soluble groups notprotected by a group which splits off by the effect of an acid. Thecontent is preferably from 0.01 to 0.7, more preferably from 0.05 to0.50, still more preferably from 0.05 to 0.40.

In the case of irradiating the positive photosensitive composition ofthe present invention with ArF excimer laser light, the resin as thecomponent (B) is preferably a resin having a monocyclic or polycyclicalicyclic hydrocarbon structure and undergoing decomposition under theaction of an acid to increase the solubility in an alkali developer.

The resin having a monocyclic or polycyclic alicyclic hydrocarbonstructure and undergoing decomposition under the action of an acid toincrease the solubility in an alkali developer (hereinafter sometimesreferred to as an “alicyclic hydrocarbon-based acid-decomposable resin”)is preferably a resin containing at least one repeating unit selectedfrom the group consisting of a repeating unit having a partial structurecontaining an alicyclic hydrocarbon represented by any one of thefollowing formulae (pI) to (pV), and a repeating unit represented by thefollowing formula (II-AB):

wherein

R₁₁ represents a methyl group, an ethyl group, an n-propyl group, anisopropyl group, an n-butyl group, an isobutyl group or a sec-butylgroup,

Z represents an atomic group necessary for forming a cycloalkyl grouptogether with the carbon atom,

R₁₂ to R₁₆ each independently represents a linear or branched alkylgroup having a carbon number of 1 to 4 or a cycloalkyl group, providedthat at least one of R₁₂ to R₁₄ or either one of R₁₅ and R₁₆ representsa cycloalkyl group,

R₁₇ to R₂, each independently represents a hydrogen atom, a linear orbranched alkyl group having a carbon number of 1 to 4 or a cycloalkylgroup, provided that at least one of R₁₇ to R₂₁ represents a cycloalkylgroup and that either one of R₁₉ and R₂₁ represents a linear or branchedalkyl group having a carbon number of 1 to 4 or a cycloalkyl group,

R₂₂ to R₂₅ each independently represents a hydrogen atom, a linear orbranched alkyl group having a carbon number of 1 to 4, or a cycloalkylgroup, provided that at least one of R₂₂ to R₂₅ represents a cycloalkylgroup, and

R₂₃ and R₂₄ may combine with each other to form a ring.

wherein

R₁₁′ and R₁₂′ each independently represents a hydrogen atom, a cyanogroup, a halogen atom or an alkyl group, and

Z′ represents an atomic group for forming an alicyclic structure,containing two bonded carbon atoms (C—C).

Formula (II-AB) is preferably the following formula (II-AB1) or(II-AB2).

In formulae (II-AB1) and (II-AB2),

R₁₃′ to R₁₆′ each independently represents a hydrogen atom, a halogenatom, a cyano group, a hydroxyl group, —COOH, —COOR₅, a group capable ofdecomposing under the action of an acid, —C(═O)—X-A′-R₁₇′, an alkylgroup or a cycloalkyl group, and at least two members out of R₁₃′ toR₁₆′ may combine to form a ring,

R₅ represents an alkyl group, a cycloalkyl group or a group having alactone structure,

X represents an oxygen atom, a sulfur atom, —NH—, —NHSO₂— or —NHSO₂NH—,

A′ represents a sing bond or a divalent linking group,

R₁₇′ represents —COOH, —COOR₅, —CN, a hydroxyl group, an alkoxy group,—CO—NH—R₆, —CO—NH—SO₂—R₆ or a group having a lactone structure,

R₆ represents an alkyl group or a cycloalkyl group, and

n represents 0 or 1.

In formulae (pI) to (pV), the alkyl group of R₁₂ to R₂₅ is a linear orbranched alkyl group having from 1 to 4 carbon atoms, and examplesthereof include a methyl group, an ethyl group, a propyl group, ann-butyl group, a sec-butyl group and a tert-butyl group.

The cycloalkyl group of R₁₂ to R₂₅ and the cycloalkyl group formed by Ztogether with the carbon atom may be monocyclic or polycyclic. Specificexamples thereof include a group having a monocyclic, bicyclic,tricyclic or tetracyclic structure with a carbon number of 5 or more.The carbon number thereof is preferably from 6 to 30, more preferablyfrom 7 to 25. These cycloalkyl groups each may have a substituent.

Preferred examples of the cycloalkyl group include an adamantyl group, anoradamantyl group, a decalin residue, a tricyclodecanyl group, atetracyclododecanyl group, a norbornyl group, a cedrol group, acyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctylgroup, a cyclodecanyl group and a cyclododecanyl group. Among these,more preferred are an adamantyl group, a norbornyl group, a cyclohexylgroup, a cyclopentyl group, a tetracyclododecanyl group and atricyclodecanyl group.

These alkyl group and cycloalkyl group each may further have asubstituent. Examples of the substituent which the alkyl group andcycloalkyl group may further have include an alkyl group (having acarbon number of 1 to 4), a halogen atom, a hydroxyl group, an alkoxygroup (having a carbon number of 1 to 4), a carboxyl group and analkoxycarbonyl group (having a carbon number of 2 to 6). These alkylgroup, alkoxy group, alkoxycarbonyl group and the like each may furtherhave a substituent. Examples of the substituent which the alkyl group,alkoxy group, alkoxycarbonyl group and the like may further have includea hydroxyl group, a halogen atom and an alkoxy group.

The structures represented by formulae (pI) to (pV) each can be used forthe protection of an alkali-soluble group in the resin. Examples of thealkali-soluble group include various groups known in this technicalfield.

Specific examples thereof include a structure where the hydrogen atom ofa carboxylic acid group, a sulfonic acid group, a phenol group or athiol group is replaced by the structure represented by any one offormulae (pI) to (pV). A structure where the hydrogen atom of acarboxylic acid group or a sulfonic acid group is replaced by thestructure represented by any one of formulae (pI) to (pV) is preferred.

The repeating unit having an alkali-soluble group protected by thestructure represented by any one of formulae (pI) to (pV) is preferablya repeating unit represented by the following formula (pA):

In formula (pA), R represents a hydrogen atom, a halogen atom or alinear or branched alkyl group having a carbon number of 1 to 4, and aplurality of R's may be the same or different.

A represents a single bond, or one group or a combination of two or moregroups, selected from the group consisting of an alkylene group, anether group, a thioether group, a carbonyl group, an ester group, anamido group, a sulfonamido group, a urethane group and a urea group. Ais preferably a single bond.

Rp₁ represents any one group of formulae (pI) to (pV).

The repeating unit represented by formula (pA) is most preferably arepeating unit comprising a 2-alkyl-2-adamantyl(meth)acrylate or adialkyl(1-adamantyl)methyl (meth)acrylate.

Specific examples of the repeating unit represented by formula (pA) areset forth below.

In the formulae above, Rx represents H, CH₃, CF₃ or CH₂OH, and Rxa andRxb each independently represents an alkyl group having a carbon numberof 1 to 4.

Examples of the halogen atom of R₁₁′ and R₁₂′ in formula (II-AB) includea chlorine atom, a bromine atom, a fluorine atom and an iodine atom.

The alkyl group of R₁₁′ and R₁₂′ is preferably a linear or branchedalkyl group having a carbon number of 1 to 10, and examples thereofinclude a methyl group, an ethyl group, an n-propyl group, an isopropylgroup and a linear or branched butyl, pentyl, hexyl or heptyl group.

The atomic group of Z′ for forming an alicyclic structure is an atomicgroup for forming, in the resin, an alicyclic hydrocarbon repeating unitwhich may have a substituent, and among these atomic groups, an atomicgroup for forming a crosslinked alicyclic structure to form acrosslinked alicyclic hydrocarbon repeating unit is preferred.

Examples of the skeleton of the alicyclic hydrocarbon formed include thesame as those of the cycloalkyl group of R₁₂ to R₂₅ in formulae (pI) to(pVI).

The alicyclic hydrocarbon skeleton may have a substituent, and examplesof the substituent include R₁₃′ to R₁₆′ in formulae (II-AB1) and(II-AB2).

In the alicyclic hydrocarbon-based acid-decomposable resin for use inthe present invention, the group capable of decomposing under the actionof an acid may be contained in at least one repeating unit out of therepeating unit having a partial structure containing an alicyclichydrocarbon represented by any one of formulae (pI) to (pV), therepeating unit represented by formula (II-AB), and the repeating unitcomprising a copolymerization component which is described later.

Various substituents R₁₃′ to R₁₆′ in formulae (II-AB1) and (II-AB2) maywork out to the substituents of an atomic group for forming an alicyclicstructure in formula (II-AB) or an atomic group Z for forming acrosslinked alicyclic structure.

Specific examples of the repeating units represented by formulae(II-AB1) and (II-AB2) are set forth below, but the present invention isnot limited thereto.

The alicyclic hydrocarbon-based acid-decomposable resin for use in thepresent invention preferably has a repeating unit having a lactonegroup. As for the lactone group, any group may be used as long as it hasa lactone structure, but a group having a 5-, 6- or 7-membered ringlactone structure is preferred. The 5-, 6- or 7-membered ring structureis preferably condensed with another ring structure in the form offorming a bicyclo structure or a spiro structure. The alicyclichydrocarbon-based acid-decomposable resin for use in the presentinvention more preferably has a repeating unit containing a group havinga lactone structure represented by any one of the following formulae(LC1-1) to (LC1-16). The group having a lactone structure may be bondeddirectly to the main chain. Among these lactone structures, (LC1-1),(LC1-4), (LC1-5), (LC1-6), (LC1-13) and (LC1-14) are preferred. By usinga specific lactone structure, the line edge roughness and thedevelopment defect are improved.

The lactone structure moiety may or may not have a substituent (Rb₂).Preferred examples of the substituent (Rb₂) include an alkyl grouphaving a carbon number of 1 to 8, a cycloalkyl group having a carbonnumber of 4 to 7, an alkoxy group having a carbon number of 1 to 8, analkoxycarbonyl group having a carbon number of 1 to 8, a carboxyl group,a halogen atom, a hydroxyl group, a cyano group and an acid-decomposablegroup. n₂ represents an integer of 0 to 4. When n₂ is an integer of 2 ormore, the plurality of Rb₂'s may be the same or different, and Rb₂'s maycombine with each other to form a ring.

Examples of the repeating unit having a lactone structure represented byany one of formulae (LC1-1) to (LC1-16) include a repeating unit whereat least one of R₁₃′ to R₁₆′ in formula (II-AB1) or (II-AB2) has a grouprepresented by any one of formulae (LC1-1) to (LC1-16) (for example, R₅of —COOR₅ is a group represented by any one of formulae (LC1-1) to(LC1-16)), and a repeating unit represented by the following formula(AI):

In formula (AI), Rb₀ represents a hydrogen atom, a halogen atom or analkyl group having a carbon number of 1 to 4.

Examples of the alkyl group of Rb₀ include a methyl group, an ethylgroup, a propyl group, an n-butyl group, a sec-butyl group and atert-butyl group. The alkyl group of Rb₀ may have a substituent.Preferred examples of the substituent which the alkyl group of Rb₀ mayhave include a hydroxyl group and a halogen atom.

Examples of the halogen atom of Rb₀ include a fluorine atom, a chlorineatom, a bromine atom and an iodine atom. Rb₀ is preferably a hydrogenatom or a methyl group.

Ab represents an alkylene group, a divalent linking group having amonocyclic or polycyclic alicyclic hydrocarbon structure, a single bond,an ether group, an ester group, a carbonyl group, a carboxyl group, or adivalent group comprising a combination thereof, preferably a singlebond or a linking group represented by -Ab₁-CO₂—.

Ab₁ is a linear or branched alkylene group or a monocyclic or polycycliccycloalkylene group, preferably a methylene group, an ethylene group, acyclohexyl residue, an adamantyl residue or a norbornyl residue.

V represents a group represented by any one of formulae (LC1-1) to(LC1-16).

The repeating unit having a lactone structure usually has an opticalisomer, but any optical isomer may be used. One optical isomer may beused alone or a mixture of a plurality of isomers may be used. In thecase of mainly using one optical isomer, the optical purity (ee) thereofis preferably 90 or more, more preferably 95 or more.

Specific examples of the repeating unit containing a group having alactone structure are set forth below, but the present invention is notlimited thereto.

(In formulae, Rx is H, CH₃, CH₂OH or CF₃.)

(In formulae, Rx is H, CH₃, CH₂OH or CF₃.)

(In formulae, Rx is H, CH₃, CH₂OH or CF₃.)

The alicyclic hydrocarbon-based acid-decomposable resin for use in thepresent invention preferably contains a repeating unit having analicyclic hydrocarbon structure substituted by a polar group. By havingthis repeating unit, the adhesion to substrate and the affinity fordeveloper are enhanced. The polar group is preferably a hydroxyl groupor a cyano group.

Examples of the alicyclic hydrocarbon structure represented by a polargroup include a structure represented by the following formula (VIIa) or(VIIb):

In formula (VIIa), R_(2c) to R_(4c) each independently represents ahydrogen atom, a hydroxyl group or a cyano group, provided that at leastone of R_(2c) to R_(4c) represents a hydroxyl group or a cyano group.Preferably, one or two members out of R_(2c) to R_(4c) is a hydroxylgroup with the remaining being a hydrogen atom, and more preferably, twomembers out of R_(2c) to R_(4c) are a hydroxyl group with the remainingbeing a hydrogen atom.

The group represented by formula (VIIa) is preferably a dihydroxy formor a monohydroxy form, more preferably a dihydroxy form.

Examples of the repeating unit having a group represented by formula(VIIa) or (VIIb) include a repeating unit where at least one of R₁₃′ toR₁₆′ in formula (II-AB1) or (II-AB2) has a group represented by formula(VIIa) or (VIIb) (for example, where R₅ in —COOR₅ is a group representedby formula (VIIa) or (VIIb)), and a repeating unit represented by thefollowing formula (AIIa) or (AIIb):

In formulae (AIIa) and (AIIb), R_(1c) represents a hydrogen atom, amethyl group, a trifluoromethyl group or a hydroxymethyl group.

R_(2c) to R_(4c) have the same meanings as R_(2c) to R_(4c) in formula(VIIa).

Specific examples of the repeating unit having an alicyclic hydrocarbonstructure substituted by a polar group, represented by formula (AIIa) or(AIIb), are set forth below, but the present invention is not limitedthereto.

The alicyclic hydrocarbon-based acid-decomposable resin for use in thepresent invention may contain a repeating unit represented by thefollowing formula (VIII):

In formula (VIII), Z₂ represents —O— or —N(R₄₁)—. R₄₁ represents ahydrogen atom, a hydroxyl group, an alkyl group or —OSO₂—R₄₂. R₄₂represents an alkyl group, a cycloalkyl group or a camphor residue. Thealkyl group of R₄₁ and R₄₂ may be substituted by a halogen atom(preferably a fluorine atom) or the like.

Specific examples of the repeating unit represented by formula (VIII)are set forth below, but the present invention is not limited thereto.

The alicyclic hydrocarbon-based acid-decomposable resin for use in thepresent invention preferably contains a repeating unit having analkali-soluble group, more preferably a repeating unit having a carboxylgroup. By containing such a repeating unit, the resolution increases inusage of forming contact holes. The repeating unit having a carboxylgroup is preferably a repeating unit where a carboxyl group is directlybonded to the resin main chain, such as repeating unit by an acrylicacid or a methacrylic acid, or a repeating unit where a carboxyl groupis bonded to the resin main chain through a linking group. The linkinggroup may have a monocyclic or polycyclic hydrocarbon structure. Anacrylic acid and a methacrylic acid are most preferred.

The alicyclic hydrocarbon-based acid-decomposable resin for use in thepresent invention may contain a repeating unit having from 1 to 3 groupsrepresented by the following formula (F1). By containing this repeatingunit, the line edge roughness performance is enhanced.

In formula (F1), R₅₀ to R₅₅ each independently represents a hydrogenatom, a fluorine atom or an alkyl group, provided that at least one ofR₅₀ to R₅₅ is a fluorine atom or an alkyl group with at least onehydrogen atom being substituted by a fluorine atom.

Rx represents a hydrogen atom or an organic group (preferably anacid-decomposable protective group, an alkyl group, a cycloalkyl group,an acyl group or an alkoxycarbonyl group).

The alkyl group of R₅₀ to R₅₅ may be substituted by a halogen atom(e.g., fluorine), a cyano group or the like, and is preferably an alkylgroup having a carbon number of 1 to 3, such as methyl group andtrifluoromethyl group.

It is preferred that R₅₀ to R₅₅ all are a fluorine atom.

The organic group represented by Rx is preferably an acid-decomposablegroup or an alkyl, cycloalkyl, acyl, alkylcarbonyl, alkoxycarbonyl,alkoxycarbonylmethyl, alkoxymethyl or 1-alkoxyethyl group which may havea substituent.

The repeating unit having a group represented by formula (F1) ispreferably a repeating unit represented by the following formula (F2):

In formula (F2), Rx represents a hydrogen atom, a halogen atom or analkyl group having a carbon number of 1 to 4. Preferred examples of thesubstituent which the alkyl group of Rx may have include a hydroxylgroup and a halogen atom.

Fa represents a single bond or a linear or branched alkylene group andis preferably a single bond.

Fb represents a monocyclic or polycyclic hydrocarbon group.

Fc represents a single bond or a linear or branched alkylene group andis preferably a single bond or a methylene group.

F₁ represents a group represented by formula (F1).

p₁ represents a number of 1 to 3.

The cyclic hydrocarbon group in Fb is preferably a cyclopentyl group, acyclohexyl group or a norbornyl group.

Specific examples of the repeating unit having a structure of formula(F1) are set forth below.

The alicyclic hydrocarbon-based acid-decomposable resin for use in thepresent invention may contain, in addition to the above-describedrepeating units, various repeating structural units for the purpose ofcontrolling the dry etching resistance, suitability for standarddeveloper, adhesion to substrate, resist profile and propertiesgenerally required of the resist, such as resolving power, heatresistance and sensitivity.

Examples of such a repeating structural unit include; but are notlimited to, repeating structural units corresponding to the monomersdescribed below.

By containing such a repeating structural unit, the performance requiredof the alicyclic hydrocarbon-based acid-decomposable resin,particularly,

(1) solubility in the coating solvent,

(2) film-forming property (glass transition point),

(3) alkali developability,

(4) film loss (selection of hydrophilic, hydrophobic or alkali-solublegroup),

(5) adhesion of unexposed part to substrate,

(6) dry etching resistance

and the like, can be subtly controlled.

Examples of the monomer include a compound having oneaddition-polymerizable unsaturated bond, selected from acrylic acidesters, methacrylic acid esters, acrylamides, methacrylamides, allylcompounds, vinyl ethers and vinyl esters.

Other than these, an addition-polymerizable unsaturated compoundcopolymerizable with the monomer corresponding to the above-describedvarious repeating structural units may be copolymerized.

In the alicyclic hydrocarbon-based acid-decomposable resin, the molarratio of respective repeating structural units contained isappropriately determined to control the dry etching resistance ofresist, suitability for standard developer, adhesion to substrate,resist profile and performances generally required of the resist, suchas resolving power, heat resistance and sensitivity.

The preferred embodiment of the alicyclic hydrocarbon-basedacid-decomposable resin for use in the present invention includes thefollowings:

(1) a resin containing a repeating unit having an alicyclichydrocarbon-containing partial structure represented by any one offormulae (pI) to (pV) (side chain type), preferably containing arepeating unit by a (meth)acrylate having a structure represented by anyone of formulae (pI) to (pV), and

(2) a resin containing a repeating unit represented by formula (II-AB)(main chain type).

The resin of (2) further includes:

(3) a resin having a repeating unit represented by formula (II-AB), amaleic anhydride derivative structure and a (meth)acrylate structure(hybrid type).

In the alicyclic hydrocarbon-based acid-decomposable resin, the contentof the repeating unit having an acid-decomposable group is preferablyfrom 10 to 60 mol %, more preferably from 20 to 50 mol %, still morepreferably from 25 to 40 mol %, based on all repeating structural units.

In the alicyclic hydrocarbon-based acid-decomposable resin, the contentof the repeating unit having an alicyclic hydrocarbon-containing partialstructure represented by any one of formulae (pI) to (pV) is preferablyfrom 25 to 70 mol %, more preferably from 35 to 65 mol %, still morepreferably from 40 to 60 mol %, based on all repeating structural units.

In the alicyclic hydrocarbon-based acid-decomposable resin, the contentof the repeating unit represented by formula (II-AB) is preferably from10 to 60 mol %, more preferably from 15 to 55 mol %, still morepreferably from 20 to 50 mol %, based on all repeating structural units.

In the resin, the content of the repeating unit based on the monomer asthe further copolymerization component can also be appropriatelyselected according to the desired resist performance, but the contentthereof is preferably 99 mol % or less, more preferably 90 mol % orless, still more preferably 80 mol % or less, based on the total molarnumber of the repeating structural unit having an alicyclichydrocarbon-containing partial structure represented by any one offormulae (pI) to (pV) and the repeating unit represented by formula(II-AB).

When the composition of the present invention is used for exposure withArF, the resin preferably has no aromatic group in view of thetransparency to ArF light.

The alicyclic hydrocarbon-based acid-decomposable resin for use in thepresent invention is preferably a resin where all repeating unitscomprise a (meth)acrylate repeating unit. In this case, the repeatingunits may be all a methacrylate, all an acrylate, or a mixture ofmethacrylate/acrylate, but the content of the acrylate repeating unit ispreferably 50 mol % or less based on all repeating units.

The alicyclic hydrocarbon-based acid-decomposable resin for use in thepresent invention is more preferably a ternary copolymerization polymercomprising from 25 to 50% of the repeating unit having an alicyclichydrocarbon-containing partial structure represented by any one offormulae (pI) to (pV), from 25 to 50% of the repeating unit having alactone structure and from 5 to 30% of the repeating unit having analicyclic hydrocarbon structure substituted by a polar group, or aquaternary copolymerization polymer additionally comprising from 5 to20% of the repeating unit having a carboxyl group or a structurerepresented by formula (F1).

The alicyclic hydrocarbon-based acid-decomposable resin for use in thepresent invention can be synthesized by an ordinary method (for example,radical polymerization). Examples of the synthesis method in generalinclude a batch polymerization method of dissolving the monomer speciesand an initiator in a solvent and heating the solution, therebyeffecting the polymerization, and a dropping polymerization method ofadding dropwise a solution containing monomer species and an initiatorin a heated solvent over 1 to 10 hours. A dropping polymerization methodis preferred. Examples of the reaction solvent include tetrahydrofuran,1,4-dioxane, ethers (e.g., diisopropyl ether), ketones (e.g., methylethyl ketone, methyl isobutyl ketone), an ester solvent (e.g., ethylacetate), an amide solvent (e.g., dimethylformamide, diethylacetamide),and a solvent capable of dissolving the composition of the presentinvention, which is described later, such as propylene glycol monomethylether acetate, propylene glycol monomethyl ether and cyclohexanone. Thepolymerization is preferably performed by using the same solvent as thesolvent used in the photosensitive composition of the present invention.By the use of this solvent, generation of particles during storage canbe suppressed.

The polymerization reaction is preferably performed in an inert gasatmosphere such as nitrogen or argon. The polymerization is started byusing a commercially available radical initiator (e.g., azo-basedinitiator, peroxide). The radical initiator is preferably an azo-basedinitiator, and an azo-based initiator having an ester group, a cyanogroup or a carboxyl group is preferred. Preferred examples of theinitiator include azobisisobutyronitrile, azobis-dimethylvaleronitrileand dimethyl 2,2′-azobis(2-methylpropionate). The initiator is addedadditionally or in parts, if desired. After the completion of reaction,the reactant is charged into a solvent, and the desired polymer isrecovered by a method such as powder or solid recovery. The reactionconcentration is from 5 to 50 mass %, preferably from 10 to 30 mass %,and the reaction temperature is usually from 10 to 150° C., preferablyfrom 30 to 120° C., more preferably from 50 to 100° C.

In the case of using the composition of the present invention for theupper resist of a multilayer resist, the resin of the component (B)preferably has a silicon atom.

As for the resin having a silicon atom and capable of decomposing underthe action of an acid to increase the solubility in an alkali developer,a resin having a silicon atom in at least either main chain or sidechain can be used. Examples of the resin having a siloxane structure inthe side chain of resin include a copolymer of an olefin-based monomerhaving a silicon atom in the side chain and a (meth)acrylic acid-basedmonomer having a maleic anhydride and an acid-decomposable group in theside chain.

The resin having a silicon atom is preferably a resin having atrialkylsilyl structure or a monocyclic or polycyclic siloxanestructure, more preferably a resin containing a repeating unit having astructure represented by any one of the following formulae (SS-1) to(SS-4), still more preferably a resin containing a (meth)acrylic acidester-based, vinyl-based or acryl-based repeating unit having astructure represented by any one of formulae (SS-1) to (SS-4).

In formulae (SS-1) to (SS-4), Rs represents an alkyl group having acarbon number of 1 to 5 and is preferably a methyl group or an ethylgroup.

The resin having a silicon atom preferably a resin containing two ormore different repeating units having a silicon atom, more preferably aresin containing both (Sa) a repeating unit having from 1 to 4 siliconatoms and (Sb) a repeating unit having from 5 to 10 silicon atoms, stillmore preferably a resin containing at least one repeating unit having astructure represented by any one of formulae (SS-1) to (SS-3) and arepeating unit having a structure represented by formula (SS-4).

In the case of irradiating the positive photosensitive composition ofthe present invention with F₂ excimer laser light, the resin of thecomponent (B) is preferably a resin having a structure that a fluorineatom is substituted to the main chain and/or the side chain of thepolymer skeleton, and being capable of decomposing under the action ofan acid to increase the solubility in an alkali developer (hereinaftersometimes referred to as a “fluorine group-containing resin”), morepreferably a resin containing a hydroxyl group with the 1-position beingsubstituted by a fluorine atom or a fluoroalkyl group or containing agroup where the hydroxyl group with the 1-position being substituted bya fluorine atom or a fluoroalkyl group is protected by anacid-decomposable group, and still more preferably a resin having ahexafluoro-2-propanol structure or a structure that the hydroxyl groupof hexafluoro-2-propanol is protected by an acid-decomposable group. Byintroducing a fluorine atom, the transparency to far ultraviolet light,particularly F₂ (157 nm) light, can be enhanced.

Preferred examples of the fluorine group-containing resin as theacid-decomposable resin (B) include a resin having at least onerepeating unit represented by the following formulae (FA) to (FG):

In these formulae, R₁₀₀ to R₁₀₃ each independently represents a hydrogenatom, a fluorine atom, an alkyl group or an aryl group.

R₁₀₄ and R₁₀₆ each is a hydrogen atom, a fluorine atom or an alkylgroup, and at least either one of R₁₀₄ and R₁₀₆ is a fluorine atom or afluoroalkyl group. R₁₀₄ and R₁₀₆ are preferably both a trifluoromethylgroup.

R₁₀₅ is a hydrogen atom, an alkyl group, a cycloalkyl group, an acylgroup, an alkoxycarbonyl group or a group capable of decomposing underthe action of an acid.

A₁ is a single bond, a divalent linking group such as alkylene group,cycloalkylene group, alkenylene group, arylene group, —OCO—, —COO— and—CON(R₂₄)—, or a linking group containing a plurality of members out ofthese groups. R₂₄ is a hydrogen atom or an alkyl group.

R₁₀₇ and R₁₀₈ each is a hydrogen atom, a halogen atom, an alkyl group,an alkoxy group, an alkoxycarbonyl group or a group capable ofdecomposing under the action of an acid.

R₁₀₉ is a hydrogen atom, an alkyl group, a cycloalkyl group or a groupcapable of decomposing under the action of an acid.

b is 0, 1 or 2.

In formulae (FA) and (FC), R₁₀₀ and R₁₀₁ may form a ring through analkylene group (having a carbon number of 1 to 5) which may besubstituted by fluorine.

The repeating units represented by formulae (FA) to (FG) each containsat least one fluorine atom, preferably 3 or more fluorine atoms, per onerepeating unit.

In formulae (FA) to (FG), the alkyl group is, for example, an alkylgroup having a carbon number of 1 to 8, and specific preferred examplesthereof include a methyl group, an ethyl group, a propyl group, ann-butyl group, a sec-butyl group, a hexyl group, a 2-ethylhexyl groupand an octyl group.

The cycloalkyl group may be monocyclic or polycyclic. The monocyclictype is preferably a cycloalkyl group having a carbon number of 3 to 8,such as cyclopropyl group, cyclopentyl group, cyclohexyl group,cycloheptyl group and cyclooctyl group. The polycyclic type ispreferably a cycloalkyl group having a carbon number of 6 to 20, such asadamantyl group, norbornyl group, isoboronyl group, camphanyl group,dicyclopentyl group, α-pinel group, tricyclodecanyl group,tetracyclododecyl group and androstanyl group. In these monocyclic orpolycyclic cycloalkyl groups, the carbon atom may be substituted by aheteroatom such as oxygen atom.

The fluoroalkyl group is preferably a fluoroalkyl group having a carbonnumber of 1 to 12, and specific preferred examples thereof include atrifluoromethyl group, a perfluoroethyl group, a perfluoropropyl group,a perfluorobutyl group, a perfluorohexyl group, a perfluorooctyl group,a perfluorooctylethyl group and a perfluorododecyl group.

The aryl group is, for example, an aryl group having a carbon number of6 to 15, and specific preferred examples thereof include a phenyl group,a tolyl group, a dimethylphenyl group, a 2,4,6-trimethylphenyl group, anaphthyl group, an anthryl group and a 9,10-dimethoxyanthryl group.

The alkoxy group is, for example, an alkoxy group having a carbon numberof 1 to 8, and specific preferred examples thereof include a methoxygroup, an ethoxy group, an n-propoxy group, an iso-propoxy group, abutoxy group, a pentoxy group, an allyloxy group and an octoxy group.

The acyl group is, for example, an acyl group having a carbon number of1 to 10, and specific preferred examples thereof include a formyl group,an acetyl group, a propanoyl group, a butanoyl group, a pivaloyl group,an octanoyl group and a benzoyl group.

The alkoxycarbonyl group is preferably a secondary alkoxycarbonyl group,more preferably a tertiary alkoxycarbonyl group, such asi-propoxycarbonyl group, tert-butoxycarbonyl group, tert-amyloxycarbonylgroup and 1-methyl-1-cyclohexyloxycarbonyl group.

The halogen atom includes, for example, a fluorine atom, a chlorineatom, a bromine atom and an iodine atom.

The alkylene group is preferably an alkylene group having a carbonnumber of 1 to 8, such as methylene group, ethylene group, propylenegroup, butylene group, hexylene group and octylene group.

The alkenylene group is preferably an alkenylene group having a carbonnumber of 2 to 6, such as ethenylene group, propenylene group andbutenylene group.

The cycloalkylene group is preferably a cycloalkylene group having acarbon number of 5 to 8, such as cyclopentylene group and cyclohexylenegroup.

The arylene group is preferably an arylene group having a carbon numberof 6 to 15, such as phenylene group, tolylene group and naphthylenegroup.

These groups each may have a substituent, and examples of thesubstituent include those having an active hydrogen, such as alkylgroup, cycloalkyl group, aryl group, amino group, amido group, ureidogroup, urethane group, hydroxyl group and carboxyl group, a halogen atom(e.g., fluorine, chlorine, bromine, iodine), an alkoxy group (e.g.,methoxy, ethoxy, propoxy, butoxy), a thioether group, an acyl group(e.g., acetyl, propanoyl, benzoyl), an acyloxy group (e.g., acetoxy,propanoyloxy, benzoyloxy), an alkoxycarbonyl group (e.g.,methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl), a cyano group and anitro group.

The alkyl group, cycloalkyl group and aryl group include those describedabove, and the alkyl group may be further substituted by a fluorine atomor a cycloalkyl group.

Examples of the group capable of decomposing under the action of anacid, contained in the fluorine group-containing resin of the presentinvention, include —O—C(R₃₆)(R₃₇)(R₃₈), —O—C(R₃₆)(R₃₇)(OR₃₉),—O—COO—C(R₃₆)(R₃₇)(R₃₈), —O—C(R₀₁)(R₀₂)COO—C(R₃₆)(R₃₇)(R₃₈),—COO—C(R₃₆)(R₃₇)(R₃₈), —COO—C(R₃₆)(R₃₇)(OR₃₉).

R₃₆ to R₃₉ each represents an alkyl group, a cycloalkyl group, an arylgroup, an aralkyl group or an alkenyl group, and R₀₁ and R₀₂ eachrepresents a hydrogen atom, an alkyl group, a cycloalkyl group, analkenyl group (e.g., vinyl, allyl, butenyl, cyclohexenyl), an aralkylgroup (e.g., benzyl, phenethyl, naphthylmethyl), or an aryl group.

Specific preferred examples include an ether or ester group of atertiary alkyl group such as tert-butyl group, tert-amyl group,1-alkyl-1-cyclohexyl group, 2-alkyl-2-adamantyl group,2-adamantyl-2-propyl group and 2-(4-methylcyclohexyl)-2-propyl group, anacetal or acetal ester group such as 1-alkoxy-1-ethoxy group andtetrahydropyranyl group, a tert-alkylcarbonate group, and atert-alkylcarbonylmethoxy group.

Specific examples of the repeating structural units represented byformulae (FA) to (FG) are set forth below, but the present invention isnot limited thereto.

The total content of the repeating units represented by formulae (FA) to(FG) is generally from 10 to 80 mol %, preferably from 30 to 70 mol %,more preferably from 35 to 65 mol %, based on all repeating unitsconstituting the resin.

In the fluorine-containing resin, in addition to these repeatingstructural units, other polymerizable monomers may be copolymerized forenhancing the performance of the resist of the present invention.

Examples of the copolymerization monomer which can be used include acompound having one addition-polymerizable unsaturated bond, selectedfrom acrylic acid esters other than those described above, acrylamides,methacrylic acid esters, methacrylamides, allyl compounds, vinyl ethers,vinyl esters, styrenes and crotonic acid esters.

From the standpoint of enhancing the dry etching resistance, controllingthe alkali solubility and increasing the adhesion to substrate, thefluorine-containing resin preferably contains another repeating unit asa copolymerization component in addition to the above-described fluorineatom-containing repeating unit. Preferred examples of the anotherrepeating unit include:

1) a repeating unit having an alicyclic hydrocarbon structurerepresented by any one of formulae (pI) to (pVI) or formula (II-AB),specifically, repeating units 1 to 23 and repeating units [II-1] to[II-32], preferably repeating units 1 to 23 where Rx is CF₃;

2) a repeating unit having a lactone structure represented by formula(Lc) or by any one of formulae (V-1) to (V-5), specifically, repeatingunits shown above, particularly, repeating units having a grouprepresented by any one of formulae (Lc) and (V-1) to (V-4); and

3) a repeating unit derived from a maleic anhydride, a vinyl ether or avinyl compound having a cyano group, represented by the followingformula (XV), (XVI) or (XVII), specifically repeating units (C-1) to(C-15).

In these repeating units, a fluorine atom may or may not be contained.

In these formulae, R₄₁ represents an alkyl group, a cycloalkyl group, anaralkyl group or an aryl group, and the alkyl group of R₄₁ may besubstituted by an aryl group.

R₄₂ represents a hydrogen atom, a halogen atom, a cyano group or analkyl group.

A₅ represents a single bond, a divalent alkylene, alkenylene,cycloalkylene or arylene group, —O—CO—R₂₂, —CO—O—R₂₃— or—CO—N(R₂₄)—R₂₅—.

R₂₂, R₂₃ and R₂₅, which may be the same or different, each represents asingle bond or a divalent alkylene, alkenylene, cycloalkylene or arylenegroup which may have an ether group, an ester group, an amide group, aurethane group or a ureido group.

R₂₄ represents a hydrogen atom, an alkyl group, a cycloalkyl group, anaralkyl group or an aryl group.

Examples of each substituent include the same as those described abovefor the substituents of formulae (FA) to (FG).

Specific examples of the repeating structural units represented byformulae (XV) to (XVII) are set forth below, but the present inventionis not limited thereto.

The total amount of the repeating unit represented by any one offormulae (XV) to (XVII) and the another repeating unit is generally from0 to 70 mol %, preferably from 10 to 60 mol %, more preferably from 20to 50 mol %, based on all repeating units constituting the resin.

The fluorine group-containing resin may contain an acid-decomposablegroup in any repeating unit.

The content of the repeating unit having an acid-decomposable group ispreferably from 10 to 70 mol %, more preferably from 20 to 60 mol %,still more preferably from 30 to 60 mol %, based on all repeating units.

The fluorine group-containing resin can be synthesized by radicalpolymerization almost in the same manner as the alicyclichydrocarbon-based acid-decomposable resin.

The weight average molecular weight of the resin as the component (B) ispreferably from 2,000 to 200,000 in terms of polystyrene by the GPCmethod. With a weight average molecular weight of 2,000 or more, heatresistance and dry etching resistance can be increased and with a weightaverage molecular weight of 200,000 or less, developability can beenhanced and at the same time, by virtue of decrease in the viscosity,the film-forming property can be improved. The molecular weight is morepreferably from 5,000 to 50,000, still more preferably from 7,000 to30,000. By controlling the molecular weight, the composition can besatisfied in all of heat resistance, resolving power, development defectand the like. The dispersity (Mw/Mn) of the resin as the component (B)is preferably from 1.0 to 3.0, more preferably from 1.2 to 2.5, stillmore preferably from 1.2 to 1.6. By controlling the dispersity to anappropriate range, the line edge roughness performance can be enhanced.

In the positive photosensitive composition of the present invention, theamount of the resin as the component (B) blended in the entirecomposition is preferably from 40 to 99.99 mass %, more preferably from50 to 99 mass %, still more preferably from 80 to 96 mass %, based onthe entire solid content.

[3] (C) Dissolution Inhibiting Compound Capable of Decomposing Under theAction of an Acid to Increase the Solubility in an Alkali Developer andHaving a Molecular Weight of 3,000 or Less (Hereinafter SometimesReferred to as a “Component (C)” or “Dissolution Inhibiting Compound”)

In order to prevent reduction in the transmittance at 220 nm or less,the dissolution inhibiting compound (C) capable of decomposing under theaction of an acid to increase the solubility in an alkali developer andhaving a molecular weight of 3,000 or less is preferably an alicyclic oraliphatic compound containing an acid-decomposable group, such asacid-decomposable group-containing cholic acid derivative described inProceeding of SPIE, 2724, 355 (1996). Examples of the acid-decomposablegroup and the alicyclic structure include the same as those describedabove for the alicyclic hydrocarbon-based acid-decomposable resin.

In the case where the photosensitive composition of the presentinvention is exposed with a KrF excimer laser or irradiated withelectron beams, the dissolution inhibiting compound preferably containsa structure in which the phenolic hydroxyl group of a phenol compound isreplaced by an acid-decomposable group. The phenol compound preferablycontains from, 1 to 9 phenol skeletons, more preferably from 2 to 6phenol skeletons.

The molecular weight of the dissolution inhibiting compound for use inthe present invention is 3,000 or less, preferably from 300 to 3,000,more preferably from 500 to 2,500.

The amount of the dissolution inhibiting compound added is preferablyfrom 3 to 50 mass %, more preferably from 5 to 40 mass %, based on thesolid content of the photosensitive composition.

Specific examples of the dissolution inhibiting compound are set forthbelow, but the present invention is not limited thereto.

[4] (D) Resin Soluble in an Alkali Developer (Hereinafter SometimesReferred to as a “Component (D)” or “Alkali-Soluble Resin”)

The alkali dissolution rate of the alkali-soluble resin is preferably 20Å/sec or more, more preferably 200 Å/sec or more (Å is angstrom), asmeasured (at 23° C.) in 0.261N tetramethylammonium hydroxide (TMAH).

Examples of the alkali-soluble resin for use in the present inventioninclude, but are not limited to, novolak resin, hydrogenated novolakresin, acetone-pyrogallol resin, o-polyhydroxystyrene,m-polyhydroxystyrene, p-polyhydroxystyrene, hydrogenatedpolyhydroxystyrene, halogen- or alkyl-substituted polyhydroxystyrene, ahydroxystyrene-N-substituted maleimide copolymer, an o/p- orm/p-hydroxystyrene copolymer, polyhydroxystyrene with the hydroxyl groupbeing partially O-alkylated (for example, 5 to 30 mol % beingO-methylated, O-(1-methoxy)ethylated, O-(1-ethoxy)ethylated,O-2-tetrahydropyranylated or O-(tert-butoxycarbonyl)methylated) orO-acylated (for example, 5 to 30 mol % being o-acylated orO-(tert-butoxy)carbonylated), a styrene-maleic anhydride copolymer, astyrene-hydroxystyrene copolymer, an x-methylstyrene-hydroxystyrenecopolymer, a carboxyl group-containing methacrylic resin and aderivative thereof, and a polyvinyl alcohol derivative.

Among these alkali-soluble resins, preferred are novolak resin,o-polyhydroxystyrene, m-polyhydroxystyrene, p-polyhydroxystyrene, acopolymer thereof, alkyl-substituted polyhydroxystyrene, partiallyO-alkylated or O-acylated polyhydroxystyrene, a styrene-hydroxystyrenecopolymer and an α-methylstyrene-hydroxystyrene copolymer.

The novolak resin can be obtained by subjecting a predetermined monomeras the main component to addition condensation with an aldehyde in thepresence of an acidic catalyst.

The weight average molecular weight of the alkali-soluble resin is 2,000or more, preferably from 5,000 to 200,000, more preferably from 5,000 to100,000.

The weight average molecular weight used herein is defined as apolystyrene-reduced value measured by gel permeation chromatography.

In the present invention, two or more of these alkali-soluble resins (D)may be used in combination.

The amount of the alkali-soluble resin used is from 40 to 97 mass %,preferably from 60 to 90 mass %, based on the entire solid content ofthe photosensitive composition.

[5] (E) Acid Crosslinking Agent Capable of Crosslinking with theAlkali-Soluble Resin Under the Action of an Acid (Hereinafter SometimesReferred to as a “Component (E)” or “Crosslinking Agent”)

In the negative photosensitive composition of the present invention, acrosslinking agent is used.

The crosslinking agent may be any compound as long as it causescrosslinking of the resin soluble in an alkali developer under theaction of an acid, but the following compounds (1) to (3) are preferred:

(1) a hydroxymethyl, alkoxymethyl or acyloxymethyl form of phenolderivative,

(2) a compound having an N-hydroxymethyl group, an N-alkoxymethyl groupor an N-acyloxymethyl group, and

(3) a compound having an epoxy group.

The alkoxymethyl group is preferably an alkoxymethyl group having acarbon number of 6 or less, and the acyloxymethyl group is preferably anacyloxymethyl group having a carbon number of 6 or less.

Among these crosslinking agents, particularly preferred are set forthbelow.

In these formulae, L¹ to L⁸, which may be the same or different, eachrepresents a hydrogen atom, a hydroxymethyl group, a methoxymethylgroup, an ethoxymethyl group or an alkyl group having a carbon number of1 to 6.

The crosslinking agent is usually added in an amount of 3 to 70 mass %,preferably from 5 to 50 mass %, based on the solid content of thephotosensitive composition.

<Other Components>

[6] (F) Basic Compound

The photosensitive composition of the present invention preferablycontains (F) a basic compound so as to reduce the change of performancein aging from exposure to heating.

Preferred structures of the basic compound include structuresrepresented by the following formulae (A) to E).

In these formulae, R²⁵⁰, R²⁵¹ and R²⁵² each independently represents ahydrogen atom, an alkyl group having a carbon number of 1 to 20, acycloalkyl group having a carbon number of 3 to 20, or an aryl grouphaving a carbon number of 6 to 20, and R²⁵⁰ and R²⁵¹ may combine witheach other to form a ring. These groups each may have a substituent. Thealkyl group or cycloalkyl group having a substituent is preferably anaminoalkyl group having a carbon number of 1 to 20, an aminocycloalkylgroup having a carbon number of 3 to 20, a hydroxyalkyl group having acarbon number of 1 to 20, or a hydroxycycloalkyl group having a carbonnumber of 3 to 20.

These groups each may contain an oxygen atom, a sulfur atom or anitrogen atom in the alkyl chain.

R²⁵³, R²⁵⁴, R²⁵⁵ and R²⁵⁶ each independently represents an alkyl grouphaving a carbon number of 1 to 6 or a cycloalkyl group having a carbonnumber of 3 to 6.

Preferred examples of the compound include guanidine, aminopyrrolidine,pyrazole, pyrazoline, piperazine, aminomorpholine, aminoalkylmorpholineand piperidine, which each may have a substituent. More preferredexamples include a compound having an imidazole structure, adiazabicyclo structure, an onium hydroxide structure, an oniumcarboxylate structure, a trialkylamine structure, an aniline structureor a pyridine structure; an alkylamine derivative having a hydroxylgroup and/or an ether bond; and an aniline derivative having a hydroxylgroup and/or an ether bond.

Examples of the compound having an imidazole structure includeimidazole, 2,4,5-triphenylimidazole and benzimidazole. Examples of thecompound having a diazabicyclo structure include1,4-diazabicyclo[2,2,2]octane, 1,5-diazabicyclo[4,3,0]non-5-ene and1,8-diazabicyclo[5,4,0]undec-7-ene. Examples of the compound having anonium hydroxide structure include a triarylsulfonium hydroxide, aphenacylsulfonium hydroxide and a sulfonium hydroxide having a2-oxoalkyl group, specifically, triphenylsulfonium hydroxide,tris(tert-butylphenyl)sulfonium hydroxide, bis(tert-butylphenyl)iodoniumhydroxide, phenacylthiophenium hydroxide and 2-oxopropylthiopheniumhydroxide. Examples of the compound having an onium carboxylatestructure include a compound having an onium hydroxide structure wherethe anion moiety is converted into a carboxylate, such as acetate,adamantane-1-carboxylate and perfluoroalkyl carboxylate. Examples of thecompound having a trialkylamine structure include tri(n-butyl)amine andtri(n-octyl)amine. Examples of the aniline compound include2,6-diisopropylaniline and N,N-dimethylaniline. Examples of thealkylamine derivative having a hydroxyl group and/or an ether bondinclude ethanolamine, diethanolamine, triethanolamine andtris(methoxyethoxyethyl)amine. Examples of the aniline derivative havinga hydroxyl group and/or an ether bond includeN,N-bis(hydroxyethyl)aniline.

These basic compounds are used individually or in combination of two ormore thereof. However, when the amount of the component (A) used is 0.05mass % or more, the basic substance may or may not be used. In the caseof using the basic compound, the amount used thereof is usually from0.001 to 10 mass %, preferably from 0.01 to 5 mass %, based on the solidcontent of the photosensitive composition. The amount used is preferably0.001 mass % or more for obtaining a sufficiently high addition effectand preferably 10 mass % or less in view of sensitivity anddevelopability of unexposed part.

[7] (G) Fluorine- and/or Silicon-containing Surfactant

The photosensitive composition of the present invention preferablyfurther contains any one fluorine- and/or silicon-containing surfactant(a fluorine-containing surfactant, a silicon-containing surfactant or asurfactant containing both a fluorine atom and a silicon atom), or twoor more thereof.

When the photosensitive composition of the present invention contains afluorine- and/or silicon-containing surfactant, a resist pattern withgood sensitivity, resolution and adhesion and less development defectscan be obtained when an exposure light source of 250 nm or less,particularly 220 nm or less, is used.

Examples of the fluorine- and/or silicon-containing surfactant includesurfactants described in JP-A-62-36663, JP-A-61-226746, JP-A-61-226745,JP-A-62-170950, JP-A-63-34540, JP-A-7-230165, JP-A-8-62834,JP-A-9-54432, JP-A-9-5988, JP-A-2002-277862 and U.S. Pat. Nos.5,405,720, 5,360,692, 5,529,881, 5,296,330, 5,436,098, 5,576,143,5,294,511 and 5,824,451. The following commercially availablesurfactants each may also be used as it is.

Examples of the commercially available surfactant which can be usedinclude a fluorine-containing surfactant and a silicon-containingsurfactant, such as EFtop EF301 and EF303 (produced by Shin-Akita KaseiK.K.), Florad FC430 and 431 (produced by Sumitomo 3M Inc.), MegafacF171, F173, F176, F189 and R08 (produced by Dainippon Ink & Chemicals,Inc.), Surflon S-382, SC101, 102, 103, 104, 105 and 106 (produced byAsahi Glass Co., Ltd.), and Troysol S-366 (produced by Troy Chemical).In addition, polysiloxane polymer KP-341 (produced by Shin-Etsu ChemicalCo., Ltd.) may also be used as the silicon-containing surfactant.

Other than those known surfactants, a surfactant using a polymer havinga fluoro-aliphatic group, which is derived from a fluoro-aliphaticcompound produced by telomerization process (also called telomerprocess) or oligomerization process (also called oligomer process), maybe used. The fluoro-aliphatic compound can be synthesized by the methoddescribed in JP-A-2002-90991.

The polymer having a fluoro-aliphatic group is preferably a copolymer ofa fluoro-aliphatic group-containing monomer with(poly(oxyalkylene))acrylate and/or (poly(oxyalkylene))methacrylate, andthe polymer may have an irregular distribution or may be a blockcopolymer. Examples of the poly(oxyalkylene) group include apoly(oxyethylene) group, a poly(oxypropylene) group and apoly(oxybutylene group). This group may also be a unit having alkylenesdiffering in the chain length within the same chain, such asblock-linked poly(oxyethylene, oxypropylene and oxyethylene) andblock-linked poly(oxyethylene and oxypropylene). Furthermore, thecopolymer of a fluoro-aliphatic group-containing monomer and a(poly(oxyalkylene))acrylate (or methacrylate) may be not only a binarycopolymer but also a ternary or greater copolymer obtained bysimultaneously copolymerizing two or more different fluoro-aliphaticgroup-containing monomers or two or more different(poly(oxyalkylene))acrylates (or methacrylates).

Examples thereof include commercially available surfactants such asMegafac F178, F-470, F-473, F-475, F-476 and F-472 (produced byDainippon Ink & Chemicals, Inc.). Other examples include a copolymer ofan acrylate (or methacrylate) having a C₆F₁₃ group with a(poly(oxyalkylene))acrylate (or methacrylate), a copolymer of anacrylate (or methacrylate) having a C₆F₁₃ group with a(poly(oxyethylene))acrylate (or methacrylate) and a(poly(oxypropylene))acrylate (or methacrylate), a copolymer of anacrylate (or methacrylate) having a C₈F₁₇ group with a(poly(oxyalkylene))acrylate (or methacrylate), and a copolymer of anacrylate (or methacrylate) having a C₈F₁₇ group with a(poly(oxyethylene))acrylate (or methacrylate) and a(poly(oxypropylene))acrylate (or methacrylate).

The amount of the fluorine- and/or silicon-containing surfactant used ispreferably from 0.0001 to 2 mass %, more preferably from 0.001 to 1 mass%, based on the entire amount of the photosensitive composition(excluding the solvent).

[8] (H) Organic Solvent

In the photosensitive composition of the present invention, theabove-described components are used by dissolving these in apredetermined organic solvent.

Examples of the organic solvent which can be used include ethylenedichloride, cyclohexanone, cyclopentanone, 2-heptanone, γ-butyrolactone,methyl ethyl ketone, ethylene glycol monomethyl ether, ethylene glycolmonoethyl ether, 2-methoxyethyl acetate, ethylene glycol monoethyl etheracetate, propylene glycol monomethyl ether, propylene glycol monomethylether acetate, toluene, ethyl acetate, methyl lactate, ethyl lactate,methyl methoxypropionate, ethyl ethoxypropionate, methylpyruvate, ethylpyruvate, propyl pyruvate, N,N-dimethylformamide, dimethylsulfoxide,N-methylpyrrolidone and tetrahydrofuran.

(Ha) Ketone-based Solvent

The solvent for use in the present invention is preferably a solventhaving at least one ketone structure.

The solvent having a ketone structure includes a chain ketone solventand a cyclic ketone solvent. A compound having a total carbon number of5 to 8 is preferred, because good coatability is obtained.

Examples of the chain ketone solvent include 2-heptanone, methyl ethylketone and methyl isobutyl ketone, with 2-heptanone being preferred.

Examples of the cyclic ketone solvent include cyclopentanone,3-methyl-2-cyclopentanone, cyclohexanone, 2-methylcyclohexanone,2,6-dimethylcyclohexanone, cycloheptanone, cyclooctanone and isophorone,with cyclohexanone and cycloheptanone being preferred.

A solvent having a ketone structure may be used alone as the solvent ormay be used as a mixed solvent with another solvent. Examples of thesolvent mixed (solvent used in combination) include a propylene glycolmonoalkyl ether carboxylate, an alkyl lactate, a propylene glycolmonoalkyl ether, an alkyl alkoxypropionate and a lactone compound.

Examples of the propylene glycol monoalkyl ether carboxylate includepropylene glycol monomethyl ether acetate, propylene glycol monomethylether propionate and propylene glycol monoethyl ether acetate.

Examples of the alkyl lactate include methyl lactate and ethyl lactate.

Examples of the propylene glycol monoalkyl ether include propyleneglycol monomethyl ether and propylene glycol monoethyl ether.

Examples of the alkyl alkoxypropionate include methyl methoxypropionate,ethyl methoxypropionate, methyl ethoxypropionate and ethylethoxypropionate.

Examples of the lactone compound include γ-butyrolactone.

The solvent used in combination is preferably propylene glycol monoalkylether carboxylate, alkyl lactate or propylene glycol monoalkyl ether,more preferably propylene glycol monomethyl ether acetate.

By mixing the ketone-based solvent and the solvent used in combination,for example, adhesion to substrate, developability and DOF are improved.

The ratio (by mass) of the ketone-based solvent and the solvent used incombination is preferably from 10/90 to 95/5, more preferably from 20/80to 80/20, still more preferably from 30/70 to 70/30.

From the standpoint of enhancing the film thickness uniformity ordevelopment defect performance, a high boiling point solvent having aboiling point of 200° C. or more, such as ethylene carbonate andpropylene carbonate, may be mixed.

The amount added of the high boiling point solvent is usually from 0.1to 15 mass %, preferably from 0.5 to 10 mass %, more preferably from 1to 5 mass %, based on the entire solvent.

By using such a ketone-based solvent alone or using a mixed solvent withanother solvent, a photosensitive composition having a solid contentconcentration of usually from 3 to 25 mass %, preferably from 5 to 22mass %, more preferably from 5 to 15 mass %, is prepared.

<Other Additives>

The photosensitive composition of the present invention may furthercontain, for example, a dye, a plasticizer, a surfactant other than thecomponent (G), a photosensitizer and a compound capable of acceleratingthe solubility in a developer, if desired.

The compound capable of accelerating the dissolution in a developer,which can be used in the present invention, is a low molecular compoundcontaining two or more phenolic OH groups or one or more carboxy groupand having a molecular weight of 1,000 or less. In the case ofcontaining a carboxyl group, an alicyclic or aliphatic compound ispreferred.

The amount added of the dissolution accelerating compound is preferablyfrom 2 to 50 mass %, more preferably from 5 to 30 mass %, based on theresin of component (B) or the resin of component (D). The amount addedis preferably 50 mass % or less from the standpoint of preventing thedevelopment residue or deformation of pattern at the development.

The phenol compound having a molecular weight of 1,000 or less can beeasily synthesized by one skilled in the art by referring to the methoddescribed, for example, in JP-A-4-122938, JP-A-2-28531, U.S. Pat. No.4,916,210 and European Patent 219294.

Specific examples of the alicyclic or aliphatic compound having acarboxy group include, but are not limited to, a carboxylic acidderivative having a steroid structure, such as cholic acid, deoxycholicacid and lithocholic acid, an adamantane carboxylic acid derivative, anadamantane dicarboxylic acid, a cyclohexanecarboxylic acid and acyclohexanedicarboxylic acid.

In the present invention, a surfactant other than (G) the fluorine-and/or silicon-containing surfactant can also be added. Specificexamples thereof include a nonionic surfactant such as polyoxyethylenealkyl ethers, polyoxyethylene alkylallyl ethers,polyoxyethylene-polyoxypropylene block copolymers, sorbitan fatty acidesters and polyoxyethylene sorbitan fatty acid esters.

One of these surfactants may be used alone or some of these surfactantsmay be used in combination.

(Pattern Forming Method)

The photosensitive composition of the present invention is used bydissolving the above-described components in a predetermined organicsolvent, preferably a mixed solvent described above, and coating theobtained solution on a predetermined support as follows.

For example, the photosensitive composition is coated on a substrate(e.g., silicon/silicon dioxide-coated substrate) as used in theproduction of a precision integrated circuit device, by an appropriatecoating method such as spinner or coater, and dried to form aphotosensitive film.

This photosensitive film is irradiated with actinic rays or radiationthrough a predetermined mask and preferably after baking (heating),developed, whereby a good pattern can be obtained.

At the irradiation with actinic rays or radiation, the exposure may beperformed by filling a liquid having a refractive index higher than thatof air between the photosensitive film and the lens (immersionexposure). By this exposure, resolution can be elevated.

Examples of the actinic ray or radiation include infrared light, visiblelight, ultraviolet light, far ultraviolet light, X-ray and electronbeam. Among these, preferred is far ultraviolet light at a wavelength of250 nm or less, more preferably 220 nm or less. Specific examplesthereof include a KrF excimer laser (248 nm), an ArF excimer laser (193nm), an F₂ excimer laser (157 nm), an X-ray and an electron beam, withArF excimer laser, F₂ excimer laser, EUV (13 nm) and electron beam beingpreferred.

In the development step, an alkali developer is used as follows. Thealkali developer which can be used for the resist composition is analkaline aqueous solution of inorganic alkalis such as sodium hydroxide,potassium hydroxide, sodium carbonate, sodium silicate, sodiummetasilicate and aqueous ammonia, primary amines such as ethylamine andn-propylamine, secondary amines such as diethylamine anddi-n-butylamine, tertiary amines such as triethylamine andmethyldiethylamine, alcohol amines such as dimethylethanolamine andtriethanolamine, a quaternary ammonium salt such as tetramethylammoniumhydroxide and tetraethylammonium hydroxide, or cyclic amines such aspyrrole and piperidine.

In the alkali developer, alcohols and a surfactant may also be added inan appropriate amount.

The alkali concentration of the alkali developer is usually from 0.1 to20 mass %.

The pH of the alkali developer is usually from 10.0 to 15.0.

EXAMPLES

The present invention is described in greater detail below by referringto Examples, but the present invention should not be construed as beinglimited thereto.

Synthesis Example of Compound (A)

Synthesis of Compound A-1:

In a 300 mL-volume three-neck flask equipped with a 100-mL droppingfunnel and a nitrogen inlet tube, 10.0 g (31.6 mmol) of1,1,2,2,3,3-hexafluoropropane-1,3-disulfonyl difluoride was charged,then dissolved in 60 mL of THF in a nitrogen atmosphere and then stirredunder ice cooling. Subsequently, 80 mL of a THF solution containing 5.89g (31.6 mmol) of 1-BOC-piperazine and 3.20 g (31.6 mmol) oftriethylamine was added dropwise through the dropping funnel over 1hour. Following the dropwise addition, the mixed solution was stirredunder ice cooling for 1 hour and after removing the ice bath, stirred atroom temperature for 8 hours. Thereafter, 300 mL of ethyl acetate wasadded to the reaction solution, and the organic layer was washed withwater several times, concentrated and then exsiccated to obtain a whitesolid having the following structure.

Furthermore, 150 mL of methanol and 80 mL of an aqueous 1M-sodiumhydroxide solution were added to the white solid and stirred at roomtemperature for 4 hours, and thereto, 9.22 g (27 mmol) oftriphenylsulfonium bromide was added and stirred at room temperature for3 hours. Subsequently, 300 mL of chloroform was added, and the organiclayer was washed with water several times, concentrated and thenvacuum-dried to obtain 20.0 g of a transparent oil.

¹H-NMR (400 MHz, CDCl₃): δ1.47 (s, 9H), 3.50 (bs, 8H), 7.71 (m, 15H).¹⁹F-NMR (400 MHz, CDCl₃): δ−110.5 (t, 2F), −114.0 (m, 2F), −119.0 (t,2F).

Various compounds (A) were synthesized in the same manner.

<Resin (B)>

The structure, molecular weight and dispersity of the resin (B) used inExamples are shown below.

Examples 1 to 17 and Comparative Examples 1 to 3

<Preparation of Resist>

The components shown in Table 1 below were dissolved in a solvent toprepared a solution having a solid content concentration of 12 mass %;and this solution was filtered through a 0.1-μm polytetrafluoroethylenefilter or polyethylene filter to prepare a positive resist solution. Thepositive resist solution prepared was evaluated by the followingmethods. The results obtained are shown in Table 1.

<Evaluation of Resist>

On a silicon substrate treated with hexamethyldisilazane, anantireflection film DUV-42 produced by Brewer Science Co., Ltd. wasuniformly coated by a spin coater to a thickness of 600 Å, dried on ahot plate at 100° C. for 90 seconds and then dried under heating at 190°C. for 240 seconds. Thereafter, each positive resist solution was coatedby a spin coater and dried at 120° C. for 90 seconds to form a resistfilm of 0.25 μm.

The formed resist film was exposed by an ArF excimer laser stepper(manufactured by ISI, NA=0.6) through a mask and immediately after theexposure, heated on a hot plate at 120° C. for 90 seconds. Thereafter,the resist film was developed with an aqueous 2.38 mass %tetramethylammonium hydroxide solution at 23° C. for 60 seconds, rinsedwith pure water for 30 seconds and dried to obtain a line pattern.

The sensitivity was defined as the minimum irradiation energy necessaryfor resolving a 0.13-μm line (line:space=1:1).

Exposure Latitude:

Defining the optimal exposure amount as the exposure amount forreproducing a line-and-space mask pattern with a line width of 90 nm,the exposure amount width allowing for a pattern size of 90 nm±10% onvarying the exposure amount was determined, and this value was dividedby the optimal exposure amount and expressed in percentage. As the valueis larger, the fluctuation in performance due to change of exposureamount is smaller and the exposure latitude is better.

Pattern Profile:

The profile at the optimal exposure amount was observed by a scanningelectron microscope (SEM).

Pitch Dependency

The line width of an isolated pattern (line/space=1/10) at the exposureamount for reproducing a mask pattern of a 130-nm dense pattern(line/space=1/1) was evaluated and expressed by the difference (nm) from130 nm. As the value is smaller, the difference in performance betweenthe dense pattern and the isolated pattern is smaller and the pitchdependency is better.

TABLE 1 (ArF, positive) Acid Generator Acid Used in Resin, BasicSurfactant, Generator g Combination g 10 g Compound g 0.03 g Example 1A-1 0.2 z38 0.3 RA-20 PEA/TPA 0.01/0.02 W-4 Example 2 A-2 0.2 z60 0.3RA-20 PEA/DIA 0.01/0.02 W-4 Example 3 A-4 0.2 z14 0.3 RA-22 DIA 0.03 W-1Example 4 A-10 0.2 z59 0.3 RA-7 PEA 0.03 W-2 Example 5 A-12 0.3 z59 0.4RA-19 PEA/DIA 0.02/0.02 W-4 Example 6 A-15 0.2 z58 0.2 RA-7 TMEA 0.02W-2 Example 7 A-21 0.2 z61 0.4 RA-4 PEA 0.03 W-4 Example 8 A-23 0.2 z630.4 RA-6 PEA 0.02 W-4 Example 9 A-1 0.2 z58 0.3 RA-22 PEA 0.02 W-4Example 10 A-28 0.2 z60 0.3 RA-1 PEA/DIA 0.01/0.02 W-4 Example 11 A-290.3 z38 0.3 RA-22 DIA 0.02 W-2 Example 12 A-31 0.3 z38 0.3 RA-21 DIA0.02 W-4 Example 13 A-39 0.2 z61 0.3 RA-25 TMEA 0.02 W-4 Example 14 A-480.2 z14 0.3 RA-8 PEA 0.02 W-2 Example 15 A-35 0.2 z58 0.3 RA-23 DIA 0.02W-4 Example 16 A-36 0.2 z50 0.3 RA-24 PEA/DIA 0.01/0.02 W-1 Example 17A-40 0.3 z38 0.3 RA-21 DIA 0.02 W-4 Comparative TPSB 0.3 z38 0.2 RA-1PEA/DIA 0.01/0.02 W-1 Example 1 Comparative TPSPB 0.3 z14 0.3 RA-4 DAI0.02 W-4 Example 2 Comparative TPSPFBSI 0.4 z38 0.3 RA-6 PEA 0.02 W-4Example 3 Ratio by Exposure Sensitivity Solvent Mass Latitude (%) Pitchdependency (nm) Pattern Profile (mJ/cm²) Example 1 A1/B1 60/40 17.6 19.9rectangular 12.1 Example 2 A1/B1 70/30 18.2 18.3 rectangular 10.5Example 3 A1/B1 60/40 16.9 18.6 rectangular 9.8 Example 4 A1/B1 60/4018.4 26.1 rectangular 11.4 Example 5 A1/B1 80/20 17.5 20.7 rectangular8.2 Example 6 A1/A4 80/20 14.8 21.5 rectangular 7.6 Example 7 A1/B160/40 17.7 24.2 rectangular 9.1 Example 8 A1/A3 80/20 16.0 18.3rectangular 8.4 Example 9 A1/B1 60/40 16.5 21.9 rectangular 7.6 Example10 A1/A4 80/20 15.3 24.9 rectangular 6.9 Example 11 A1/B1 60/40 16.721.2 rectangular 7.7 Example 12 A1/B2 70/30 14.6 20.1 rectangular 9.0Example 13 A1/A3 60./40 18.2 23.1 rectangular 15.1 Example 14 A1/B160/40 15.1 18.7 rectangular 15.9 Example 15 A1/A3 80/20 18.1 22.5rectangular 17.2 Example 16 A1/B1 80/20 18.9 21.0 rectangular 16.8Example 17 A1/B1 60/40 16.2 23.0 rectangular 16.6 Comparative A1/B160/40 7.3 40.1 tapered 10.2 Example 1 Comparative A1/A3 60/40 7.0 35.2tapered 11.1 Example 2 Comparative A1/B1 60/40 8.9 44.4 tapered 12.6Example 3

Abbreviations common in respective Tables are shown together below.

[Acid Generator]

Abbreviations of the acid generators used in Comparative Examples are asfollows.

-   TPSH: triphenylsulfonium hexadecanesulfonate

-   TPSB: triphenylsulfonium pentafluorobenzenesulfonate

-   TPSPB: triphenylsulfonium perfluorobutanesulfonate

[Basic Compound]

-   TPI: 2,4,5-triphenylimidazole-   TPSA: triphenylsulfonium acetate-   HEP: N-hydroxyethylpiperidine-   DIA: 2,6-diisopropylaniline-   DCMA: dicyclohexylmethylamine-   TPA: tripentylamine-   HAP: hydroxyantipyrine-   TBAH: tetrabutylammonium hydroxide-   TMEA: tris(methoxyethoxyethyl)amine-   PEN: N-phenyldiethanolamine-   TOA: trioctylamine-   DBN: 1,5-diazabicyclo[4.3.0]non-5-ene    [Surfactant]-   W-1: Megafac F176 (produced by Dainipnon Ink & Chemicals, Inc.)    (fluorine-containing)-   W-2: Megafac R08 (produced by Dainippon Ink & Chemicals, Inc.)    (fluorine- and silicon-containing)-   W-3: polysiloxane polymer KP-341 (produced by Shin-Etsu Chemical    Co., Ltd.) (silicon-containing)-   W-4: Troysol S-366 (produced by Troy Chemical)    [Solvent]-   A1: propylene glycol monomethyl ether acetate-   A2: 2-heptanone-   A3: cyclohexanone-   A4: γ-butyrolactone-   B1: propylene glycol methyl ether-   B2: ethyl lactate-   [Dissolution Inhibiting Compound]-   LCB: tert-butyl lithocholate

As apparent from the results in Table 1, the photosensitive compositionof the present invention exhibits excellent property in exposurelatitude, pattern profile and pitch dependency at the ArF exposure.

In Examples 1′ and 2′, the acid generator of Examples 1 and 2 waschanged to A-32 (0.2 g). The resolution of these compositions and thecompositions of Examples 1 and 2 was verified. The resolution wasdefined as the minimum dimension (nm) of a resist pattern resolved withthe minimum irradiation energy in the evaluation of sensitivity above.

As a result, the resolutions of Examples 1, 2, 1′ and 2′ were 95 nm, 100nm, 126 nm and 135 nm, respectively.

[Evaluation of Immersion Exposure]

<Preparation of Resist>

The components of each of Examples 1 to 17 shown in Table 1 weredissolved in a solvent to prepare a solution having a solid contentconcentration of 8 mass %, and this solution was filtered through a0.1-μm polyethylene filter to prepare a positive resist solution. Theprepared positive resist solutions were evaluated by the followingmethods.

<Evaluation of Resolution>

An organic antireflection film ARC29A (produced by Nissan ChemicalIndustries, Ltd.) was coated on a silicon wafer and baked at 205° C. for60 seconds to form a 78-nm antireflection film. On this film, the resistcomposition prepared was coated and baked at 115° C. for 60 seconds toform a 150-nm resist film. The thus-obtained wafer was subjected totwo-beam interference exposure (wet exposure) by using pure water as theimmersion solution. In the two-beam interference exposure (wetexposure), as shown in FIG. 1, the wafer 10 with an antireflection filmand a resist film was exposed through a prism 8 and an immersionsolution (pure water) 9 by using a laser 1, a diaphragm 2, a shutter 3,three reflecting mirrors 4, 5 and 6, and a condenser lens 7. Thewavelength of the laser 1 used was 193 nm, and a prism of forming a65-nm line-and-space pattern 8 was used. Immediately after the exposure,the resist film was heated at 120° C. for 60 seconds, then developedwith an aqueous tetramethylammonium hydroxide solution (2.38%) for 60seconds and after rinsing with pure water, spin-dried. The obtainedresist pattern was observed by a scanning electron microscope (S-9260,manufactured by Hitachi Ltd.), as a result, a 65-nm line-and-spacepattern was resolved.

The compositions of Examples 1 to 17 were found to exhibit goodimage-forming capability even in the exposure method through animmersion solution.

Examples 18 to 23 and Comparative Examples 4 to 7

(1) Formation of Lower Resist Layer

FHi-028DD Resist (resist for i-line, produced by Fujifilm Olin Co.,Ltd.) was coated on a 6-inch silicon wafer by using a spin coater, Mark8, manufactured by Tokyo Electron Ltd. and then baked at 90° C. for 90seconds to obtain a uniform film having a thickness of 0.55 μm.

This film was further heated at 200° C. for 3 minutes to form a lowerresist layer having a thickness of 0.40 μm.

(2) Formation of Upper Resist Layer

The components shown in Table 2 below were dissolved in a solvent toprepare a solution having a solid content concentration of 11 mass %,and this solution was microfiltered through a membrane filter having apore size of 0.1 μm to prepare an upper resist composition.

The prepared upper resist composition was coated on the lower resistlayer in the same manner and heated at 130° C. for 90 seconds to form anupper resist layer having a thickness of 0.20 μm.

Resins (SI-1) to (SI-5) in Table 2 are shown below.

Molecular Weight (SI-1)

15,000 (SI-2)

14,500 (SI-3)

9,600 (SI-4)

8,900 (SI-5)

10,800(3) Evaluation of Resist

The wafer obtained above was exposed by an ArF excimer stepper 9300(manufactured by ISI) having mounted thereon a resolution mask, whilechanging the exposure amount.

Subsequently, the wafer was heated at 120° C. for 90 seconds, developedwith a tetrahydroammonium hydroxide developer (2.38 mass %) for 60seconds, rinsed with distilled water and dried to obtain an upper layerpattern. The exposure latitude, pattern profile and pitch dependencywere evaluated in the same manner as in Example 1.

The results obtained are shown in Table 2.

TABLE 2 (silicon-containing positive) Acid Generator Acid Used in Resin,Basic Surfactant, Generator G Combination g 10 g Compound g 0.03 gExample 18 A-1 0.2 z38 0.3 SI-1 PEA 0.02 W-4 Example 19 A-35 0.15 z140.2 SI-2 TMEA 0.02 W-3 Example 20 A-36 0.2 z61 0.3 SI-4 PEA 0.02 W-1Example 21 A-4 0.3 z60 0.3 SI-3 TPA 0.02 W-4 Example 22 A-15 0.3 z59 0.2SI-1 DIA 0.025 W-2 Example 23 A-21 0.15 z64 0.3 SI-5 PEA 0.02 W-4Comparative TPSB 0.3 z61 0.2 SI-1 PEA/DIA 0.01/0.02 W-4 Example 4Comparative TPSPB 0.3 z36 0.3 SI-2 TPA 0.02 W-2 Example 5 ComparativeTPSPP 0.3 z38 0.3 SI-1 PEA 0.02 W-4 Example 6 Comparative TPSPFBSI 0.4z38 0.3 SI-5 DIA 0.02 W-4 Example 7 Ratio by Exposure SensitivitySolvent Mass Latitude (%) Pitch dependency (nm) Pattern Profile (mJ/cm²)Example 18 A1/A3 60/40 18.0 22.5 rectangular 9.1 Example 19 A1 80/2017.1 22.3 rectangular 16.1 Example 20 A1/A3 90/10 16.1 22.1 rectangular16.3 Example 21 A1/A3 100 15.6 25.9 rectangular 7.8 Example 22 A1/A380/20 16.8 23.6 rectangular 8.4 Example 23 A1/A3 60/40 16.5 26.8rectangular 8.6 Comparative A1/A3 60/40 9.5 43.5 tapered 10.6 Example 4Comparative A1/A3 60/40 8.9 36.5 tapered 11.7 Example 5 ComparativeA1/A3 60/40 7.7 34.5 rectangular 9.9 Example 6 Comparative A1/A4 60/4010.1 35.5 tapered 10.8 Example 7

As apparent from the results in Table 2, the photosensitive compositionof the present invention exhibits excellent property in exposurelatitude, pattern profile and pitch dependency even when used as atwo-layer resist.

Examples 24 to 29 and Comparative Examples 8 to 11

<Preparation of Resist>

The components shown in Table 3 below were dissolved in a solvent, andthe resulting solution was filtered through a 0.1-μmpolytetrafluoroethylene filter to prepare a positive resist solutionhaving a solid content concentration of 14 mass %.

<Evaluation of Resist>

On a silicon substrate treated with hexamethyldisilazane, the preparedpositive resist solution was uniformly coated by a spin coater and driedunder heating on a hot plate at 120° C. for 90 seconds to form a resistfilm having a thickness of 0.4 μm.

The obtained resist film was exposed through a mask for a line-and-spacepattern by using a KrF excimer laser stepper (NA=0.63) and immediatelyafter the exposure, heated on a hot plate at 110° C. for 90 seconds.Thereafter, the resist film was developed with an aqueous 2.38 mass %tetramethylammonium hydroxide solution at 23° C. for 60 seconds, rinsedwith pure water for 30 seconds and then dried to form a line pattern.Thee exposure latitude, pattern profile and pitch dependency wereevaluated in the same manner as in Example 1.

The evaluation results are shown in Table 3.

TABLE 3 (KrF, positive) Acid Generator Acid Used in Resin, BasicSurfactant, Generator g Combination g 10 g Compound g 0.03 g Example 24A-1 0.18 z38 0.3 SI-1 DIA 0.02 W-4 Example 25 A-35 0.15 z14 0.3 SI-2TMEA 0.03 W-4 Example 26 A-36 0.2 z61 0.2 SI-3 DIA 0.02 W-1 Example 27A-4 0.2 z60 0.3 SI-4 PEA/DIA 0.02 W-2 Example 28 A-15 0.2 z59 0.4 SI-1TPA 0.04 W-1 Example 29 A-21 0.2 z64 0.2 SI-5 PEA 0.01/0.02 W-4Comparative TPSB 0.3 z61 0.4 SI-1 PEA/DIA 0.01/0.02 W-4 Example 8Comparative TPSPB 0.2 z14 0.3 SI-1 PEA 0.02 W-1 Example 9 ComparativeTPSPP 0.2 z38 0.3 SI-3 PEA 0.02 W-4 Example 10 Comparative TPSPFBSI 0.2z38 0.3 SI-5 DIA 0.02 W-4 Example 11 Ratio by Exposure SensitivitySolvent Mass Latitude (%) Pitch dependency (nm) Pattern Profile (mJ/cm²)Example 24 A1/B1 60/40 13.9 19.5 rectangular 12.3 Example 25 A1/A3 90/1015.7 20.5 rectangular 15.3 Example 26 A1/B1 60/40 14.7 25.0 rectangular17.3 Example 27 A1/B1 60/40 13.4 23.5 rectangular 11.5 Example 28 A1/A380/20 12.6 21.0 rectangular 10.6 Example 29 A1/B1 60/40 14.5 25.5rectangular 9.8 Comparative A1/A3 60/40 9.2 31.5 tapered 11.6 Example 8Comparative A1/A4 70/30 8.8 38.0 tapered 10.1 Example 9 ComparativeA1/B1 60/40 8.6 36.0 tapered 9.3 Example 10 Comparative A1/A4 60/40 9.939.0 tapered 10.2 Example 11

The weight average molecular weight and dispersity of each of Resins(R-1) to (R-5) used in Table 3 are shown in Table 4 below.

TABLE 4 Resin Weight Average Molecular Weight Dispersity (Mw/Mn) R-113000 1.2 R-2 11000 1.7 R-3 13000 1.2 R-4 10000 1.8 R-5 11000 1.8

As apparent from the results in Table 3, the photosensitive compositionof the present invention exhibits excellent property in exposurelatitude, pattern profile and pitch dependency even when used as apositive resist composition for exposure with a KrF excimer laser.

Examples 30 to 35 and Comparative Examples 12 to 15

<Preparation of Resist>

The components shown in Table 5 below were dissolved in a solvent, andthe resulting solution was filtered through a 0.1-μmpolytetrafluoroethylene filter to prepare a negative resist solutionhaving a solid content concentration of 14 mass %.

The prepared negative resist solutions were evaluated in the same manneras in Example 24. The results obtained are shown in Table 5.

TABLE 5 (KrF, negative) Acid Generator Acid Used in Resin, BasicSurfactant, Generator g Combination g 10 g Compound g 0.03 g Example 30A-1 0.18 z38 0.3 SI-1 h 0.02 W-4 Example 31 A-35 0.15 z14 0.3 SI-2 DIA0.02 W-3 Example 32 A-36 0.2 z61 0.2 SI-2 PEA/DIA 0.01/0.02 W-4 Example33 A-4 0.2 z60 0.3 SI-3 TPA 0.02 W-2 Example 34 A-15 0.2 z28 0.4 SI-1PEA 0.02 W-2 Example 35 A-21 0.2 z64 0.2 SI-1 TMEA 0.02 W-4 ComparativeTPSB 0.15 z14 0.2 SI-1 PEA 0.02 W-1 Example 12 Comparative TPSPB 0.3 z380.4 SI-1 DIA 0.02 W-4 Example 13 Comparative TPSPP 0.3 z59 0.5 SI-3PEA/DIA 0.01/0.02 W-4 Example 14 Comparative TPSPFBSI 0.2 z38 0.3 SI-3DIA 0.02 W-4 Example 15 Exposure Ratio by Crosslinking Latitude PatternSensitivity Solvent Mass Agent (g) (%) Pitch dependency (nm) Profile(mJ/cm²) Example 30 A1/B1 60/40 CL-1(3) 14.8 21.5 rectangular 9.4Example 31 A1/A3 60/40 CL-1(2) 16.9 25.5 rectangular 10.5 Example 32A1/A3 80/20 CL-1(2) 18.0 26.5 rectangular 11.3 Example 33 A1/B1 60/40CL-4(4) 13.4 20.5 rectangular 16.1 Example 34 A1/B1 75/25 CL-2(4) 17.119.5 rectangular 14.3 Example 35 A1/B1 60/40 CL-3(2) 16.4 23.5rectangular 17.0 Comparative A1/A3 60/40 CL-5(2) 9.4 40.5 taper 10.4Example 12 Comparative A1/A4 80/20 CL-1(2) 10.9 46.5 taper 10.0 Example13 Comparative A1/A4 60/40 CL-5(2) 10.1 44.0 taper 9.9 Example 14Comparative A1/B1 70/30 CL-1(2) 11.2 34.5 taper 12.8 Example 15

The structure, molecular weight and molecular weight distribution ofeach alkali-soluble resin in Table 5 are shown below.

Mw Mw/Mn P-1

16,000 2.30 P-2

12,000 1.2 P-3

6,000 1.2 VP-5000 produced by Nippon Soda Co., Ltd.

As apparent from the results in Table 5, the photosensitive compositionof the present invention exhibits excellent property in exposurelatitude, pattern profile and pitch dependency even when used as anegative resist composition for exposure with a KrF excimer laser.

Examples 36 to 41 and Comparative Examples 16 to 19

<Preparation of Resist>

The components shown in Table 3 were dissolved in a solvent, and theresulting solution was filtered through a 0.1-μm polytetrafluoroethylenefilter to prepare a positive resist solution having a solid contentconcentration of 12 mass %.

<Evaluation of Resist>

On a silicon substrate treated with hexamethyldisilazane, the preparedpositive resist solution was uniformly coated by a spin coater and driedunder heating on a hot plate at 120° C. for 60 seconds to form a resistfilm having a thickness of 0.3 μm.

The obtained resist film was irradiated by an electron beam projectionlithography apparatus manufactured by Nikon Corp. (accelerating voltage:100 KeV) and immediately after the irradiation, heated on a hot plate at110° C. for 90 seconds. Thereafter, the resist film was developed withan aqueous tetramethylammonium hydroxide solution having a concentrationof 2.38 mass % at 23° C. for 60 seconds, rinsed with pure water for 30seconds and then dried to form a line-and-space pattern. The exposurelatitude, pattern profile and pitch dependency were evaluated in thesame manner as in Example 1.

The evaluation results are shown in Table 6.

TABLE 6 (EB, positive) Exposure Pitch Latitude dependency PatternSensitivity (%) (nm) Profile (mJ/cm²) Example 36 14.4 21.5 rectangular10.2 Example 37 13.4 17.0 rectangular 17.3 Example 38 14.7 22.5rectangular 16.9 Example 39 14.3 18.5 rectangular 10.3 Example 40 14.520.0 rectangular 11.8 Example 41 14.2 20.5 rectangular 12.5 Comparative8.9 42.5 tapered 10.2 Example 16 Comparative 9.5 33.5 tapered 9.7Example 17 Comparative 8.7 37.0 tapered 11.8 Example 18 Comparative 9.434.5 tapered 10.8 Example 19

As apparent from the results in Table 6, the photosensitive compositionof the present invention exhibits excellent property in exposurelatitude, pattern profile and pitch dependency even when used as apositive resist composition for electron beam irradiation.

Examples 42 to 47 and Comparative Examples 20 to 23

<Preparation of Resist>

The components shown in Table 5 were dissolved in a solvent, and theresulting solution was filtered through a 0.1-μm polytetrafluoroethylenefilter to prepare a negative resist solution having a solid contentconcentration of 12 mass %.

<Evaluation of Resist>

On a silicon substrate treated with hexamethyldisilazane, the preparednegative resist solution was uniformly coated by a spin coater and driedunder heating on a hot plate at 120° C. for 60 seconds to form a resistfilm having a thickness of 0.3 μm.

The obtained resist film was irradiated by an electron beam projectionlithography apparatus manufactured by Nikon. Corp. (acceleratingvoltage: 100 KeV) and immediately after the irradiation, heated on a hotplate at 110° C. for 90 seconds. Thereafter, the resist film wasdeveloped with an aqueous tetramethylammonium hydroxide solution havinga concentration of 2.38 mass % at 23° C. for 60 seconds, rinsed withpure water for 30 seconds and then dried to form a line-and-spacepattern. The exposure latitude, pattern profile and pitch dependencywere evaluated in the same manner as in Example 1.

The evaluation results are shown in Table 7.

TABLE 7 (EB, negative) Exposure Pitch Latitude dependency PatternSensitivity (%) (nm) Profile (mJ/cm²) Example 42 15.5 21.5 rectangular10.9 Example 43 13.4 18.0 rectangular 10.6 Example 44 13.0 19.0rectangular 11.8 Example 45 14.4 20.0 rectangular 17.3 Example 46 15.021.5 rectangular 16.9 Example 47 15.3 24.0 rectangular 14.1 Comparative8.6 40.5 tapered 11.3 Example 20 Comparative 9.0 44.5 tapered 10.7Example 21 Comparative 9.3 38.0 tapered 12.0 Example 22 Comparative 8.938.5 tapered 9.9 Example 23

As apparent from the results in Table 7, the photosensitive compositionof the present invention exhibits excellent property in exposurelatitude, pattern profile and pitch dependency even when used as anegative resist composition for electron beam irradiation.

Examples 48 to 53 and Comparative Examples 24 to 27

The components shown in Table 4 were dissolved in a solvent, and theresulting solution was filtered through a 0.1 μm polytetrafluoroethylenefilter to prepare a positive resist solution having a solid contentconcentration of 8 mass %. The evaluation was performed as follows.

<Evaluation of Resist>

On a silicon substrate treated with hexamethyldisilazane, the preparedpositive resist solution was uniformly coated by a spin coater and driedunder heating on a hot plate at 120° C. for 60 seconds to form a resistfilm having a thickness of 0.15 μm, The obtained resist film wasplanarly exposed with EUV light (wavelength: 13 nm) while changing theexposure amount in 0.5-mJ steps in the range from 0 to 10.0 mJ and bakedat 110° C. for 90 seconds. Thereafter, the dissolution rate at eachexposure amount was measured by using an aqueous 2.38%tetramethylammonium hydroxide (TMAH) solution, and a sensitivity curvewas obtained from the measured values. The sensitivity was defined asthe exposure amount when the dissolution rate of resist was saturated onthe sensitivity curve. Also, the dissolution contrast (γ value) wascalculated from the gradient in the straight line part of thesensitivity curve. As the γ value is larger, the dissolution contrast isbetter.

The evaluation results are shown in Table 8 below.

TABLE 8 (EUV) Sensitivity (mJ/cm²) γ Value Example 48 2.2 10.2 Example49 1.9 11.2 Example 50 2.1 9.3 Example 51 2.2 9.7 Example 52 1.7 10.7Example 53 2.3 10.2 Comparative Example 24 3.5 8.6 Comparative Example25 3.3 7.6 Comparative Example 26 3.6 9.1 Comparative Example 27 3.8 8.1

It is seen from the results in Table 8 that the resist composition ofthe present invention is excellent by exhibiting high sensitivity andhigh contract in the characteristic evaluation by the irradiation of EUVlight as compared with the compositions of Comparative Examples.

This application is based on Japanese patent application JP 2005-015965,filed on Jan. 24, 2005, the entire content of which is herebyincorporated by reference, the same as if set forth at length.

1. A photosensitive composition comprising (A) a compound capable ofgenerating an organic acid having a bond which is cleaved by an acid,upon irradiation with actinic rays or radiation, said generated organicacid having an acid decomposable group, and the bond which is cleaved byan acid being selected from the group consisting of an acetal bond, acarbamoyl bond and a carbonate bond.
 2. The photosensitive compositionas claimed in claim 1, wherein the organic acid has a structurerepresented by the following formula (I) upon irradiation with actinicrays or radiation:


3. The photosensitive composition as claimed in claim 1, wherein theorganic acid is represented by the following formula (II) uponirradiation with actinic rays or radiation:HO₃S-A-X-B-R  (II) wherein A represents a divalent linking group, Xrepresents a single bond or —SO₂—, B represents a single bond, an oxygenatom or —N(Rx)-, Rx represents a hydrogen atom or a monovalent organicgroup, R represents a monovalent organic group containing a nitrogenatom, said nitrogen atom being substituted by the following formula(III):

R′ represents a monovalent organic group, and when B is —N(Rx)-, R andRx may combine to form a ring.
 4. The photosensitive composition asclaimed in claim 3, wherein the compound (A) capable of generating anorganic acid represented by formula (II) upon irradiation with actinicrays or radiation is a sulfonium salt compound of the formula (Al)wherein X⁻represents an anion of an organic acid represented by formula(II) or an iodonium salt compound of the formula (A2) whereinX⁻represents an anion of an organic acid represented by formula (II),

wherein in formula (A1), R₂₀₁, R₂₀₂ and R₂₀₃ each independentlyrepresents an organic group and two of them may combine to form a ringstructure which may contain an oxygen atom, a sulfur atom, an esterbond, an amide bond or a carbonyl group; and wherein in formula (A2),R₂₀₄ and R₂₀₅ each independently represents an aryl group, an alkylgroup or a cycloalkyl group.
 5. The photosensitive composition asclaimed in claim 1, which further comprises (A′) a compound capable ofgenerating an acid compound other than the organic acid, uponirradiation with actinic rays or radiation.
 6. The photosensitivecomposition as claimed in claim 5, wherein the compound (A′) is asulfonium salt of fluorine-substituted alkanesulfonic acid,fluorine-substituted benzenesulfonic acid or a fluorine-substitutedimide acid.
 7. The photosensitive composition as claimed in claim 1,which further comprises (B) a resin capable of decomposing under theaction of an acid to increase the solubility in an alkali developer. 8.The photosensitive composition as claimed in claim 7, wherein the resin(B) has a hexafluoroisopropanol structure.
 9. The photosensitivecomposition as claimed in claim 7, wherein the resin (B) has ahydroxystyrene structural unit.
 10. The photosensitive composition asclaimed in claim 7, wherein the resin (B) has at least one repeatingunit selected from 2-alkyl-2-adamantyl (meth)acrylate anddialkyl(1-adamantyl)methyl (meth)acrylate.
 11. The photosensitivecomposition as claimed in claim 7, wherein the resin (B) has amonocyclic or polycyclic alicyclic hydrocarbon structure.
 12. Thephotosensitive composition as claimed in claim 11, wherein the resin (B)further has a repeating unit having a carboxyl group.
 13. Thephotosensitive composition as claimed in claim 7, wherein the resin (B)has a repeating unit having a lactone structure.
 14. The photosensitivecomposition as claimed in claim 1, which further comprises (D) a resinsoluble in an alkali developer, and (E) an acid crossliniking agentcapable of crosslinking with the resin soluble in an alkali developerunder the action of an acid.
 15. The photosensitive composition asclaimed in claim 1, which further comprises at least one of (F) a basiccompound and (G) a fluorine-and/or silicon-containing surfacant.
 16. Thephotosensitive composition as claimed in claim 15, wherein the basiccompound (F) is a compound having a structure selected from an imidazolestructure, a diazabicyclo structure, an onium hydroxide structure, anonium carboxylate structure, a trialkylamine structure, an anilinestructure and a pyridine structure, an alkylamine derivative having ahydroxyl group and/or an ether bond, or an aniline derivative having ahydroxyl group and/or an ether bond.
 17. A pattern forming methodcomprising: forming a resist film from the photosensitive compositionclaimed in claim 1; and exposing and developing said resist film.
 18. Anorganic acid having a structure represented by the following formula (I)and a salt thereof:


19. An organic acid represented by the following formula (II) and a saltthereof:HO₃S-A-X-B-R  (II) wherein A represents a divalent linking group, Xrepresents a single bond or —SO₂—, B represents a single bond, an oxygenatom or —N(Rx)-, Rx represents a hydrogen atom or a monovalent organicgroup, R represents a monovalent organic group containing a nitrogenatom, said nitrogen atom being substituted by the following formula(III):

R′ represents a monovalent organic group, and when B is —N(Rx)-, R andRx may combine to form a ring.
 20. A sulfonium salt compound of theformula (A1) wherein X⁻represents an anion of an organic acidrepresented by the following formula (II) or an iodonium salt compoundof the formula (A2) wherein X⁻represents an anion of an organic acidrepresented by the following formula (II):HO₃S-A-X-B-R  (II) wherein A represents a divalent linking group, Xrepresents a single bond or —SO₂—, B represents a single bond, an oxygenatom or —N(Rx)-, Rx represents a hydrogen atom or a monovalent organicgroup, R represents a monovalent organic group containing a nitrogenatom, said nitrogen atom being substituted by the following formula(III):

R′ represents a monovalent organic group, and when B is —N(Rx)-, R andRx may combine to form a ring,

wherein in formula (A1), R₂₀₁, R₂₀₂ and R₂₀₃ each independentlyrepresents an organic group and two of them may combine to form a ringstructure which may contain an oxygen atom, a sulfur atom, an esterbond, an amide bond or a carbonyl group; and wherein in formula (A2),R₂₀₄ and R₂₀₅ each independently represents an aryl group, an alkylgroup or a cycloalkyl group.
 21. A photosensitive compositioncomprising: (A) a compound capable of generating an organic acid havinga bond which is cleaved by an acid, upon irradiation with actinic raysor radiation, said generated organic acid having an acid decomposablegroup, and the bond which is cleaved by an acid being selected from thegroup consisting of an amino bond, an amido bond, an ester bond, anacetal bond, a carbamoyl bond and a carbonate bond; and (B) a resincapable of decomposing under the action of an acid to increase itssolubility in an alkali developer, which has a repeating unitrepresented by formula (AI):

wherein Rb₀ represents a hydrogen atom, a halogen atom or an alkyl grouphaving a carbon number of 1 to 4; Ab represents an alkylene group, adivalent linking group having a monocyclic or polycyclic alicyclichydrocarbon structure, a single bond, a linking group represented by−Ab₁-CO₂—, an ether group, an ester group, a carbonyl group, a carboxylgroup, or a divalent group comprising a combination thereof; Ab₁ is alinear or branched alkylene group or a monocyclic or polycycliccycloalkylene group; and V represents a group represented by any one offormulae (LC1-1) to (LC1-16):

wherein Rb₂ represents a substituent selected from the group consistingof an alkyl group having a carbon number of 1 to 8, a cycloalkyl grouphaving a carbon of 4 to 7, an alkoxy group having a carbon number of 1to 8, an alkoxycarbonyl group having a carbon number of 1 to 8, acarboxyl group, a halogen atom, a hydroxyl group, a cyano group and anacid-decomposable group; n₂ represents an integer of 0 to 4, and when n₂is an integer of 2 or more, the plurality of Rb₂'s may be the same ordifferent, and Rb₂'s may combine with each other to form a ring.
 22. Thephotosensitive composition of claim 21, wherein the resin (B) has arepeating unit selected from the group consisting of the followingrepeating units 4 to 19:

wherein Rx represents H, CH₃, or CH₂OH, and Rxa and Rxb eachindependently represents an alkyl group having a carbon number of 1 to4.
 23. The photosensitive composition as claimed in claim 21, whichfurther comprises (A′) a compound capable of generating an acid compoundother than the organic acid, upon irradiation with actinic rays orradiation; and the compound (A′) is a sulfonium salt offluorine-substituted alkanesulfonic acid, fluorine-substitutedbenzenesulfonic acid or a fluorine-substituted imide acid.
 24. Thephotosensitive composition as claimed in claim 21, wherein the resin (B)has a hexafluoroisopropanol structure.
 25. The photosensitivecomposition as claimed in claim 21, which further comprises at least oneof (F) a basic compound and (G) a fluorine- and/or silicon-containingsurfactant.
 26. The photosensitive composition as claimed in claim 25,wherein the basic compound (F) is a compound having a structure selectedfrom an imidazole structure, a diazabicyclo structure, an oniumhydroxide structure, an onium carboxylate structure, a trialkylaminestructure, an aniline structure and a pyridine structure, an alkylaminederivative having a hydroxyl group and/or an ether bond, or an anilinederivative having a hydroxyl group and/or an ether bond.
 27. A patternforming method comprising: forming a resist film from the photosensitivecomposition claimed in claim 21; and exposing and developing said resistfilm.